We spend most of the time interacting with our smartphones through touchscreen interfaces. These finger-friendly menus make what could be a complicated system easier to deal with and understand. Cellphones and telephone services have been around far longer than color touchscreens, though, and there are features from the early days of mobiles still hiding in plain sight.

There were whole systems for checking how many minutes you had left on your plan for a world where you couldn’t just download a carrier app. They happened entirely through your dialer, and whatever calls or text messages you could receive. Those systems still exist today, even if most people never have to use them, and you can access them on your smartphone if you know what codes to type. Not all of them will be useful, but if you like learning about your smartphone or want to appreciate the complexity of mobile networks, they’re fun to play around with. Here are phone codes you can try on your own phone, whether it’s an Android phone or an iPhone.

What are phone codes anyway?

Most deal with the telephone features of your smartphone

While these codes are colloquially called phone codes or short codes, officially, most of them are part of GSM, or the Global System for Mobile Communications. Most phone codes fall under what’s called USSD (Unstructured Supplementary Service Data) in the GSM, or MMI (Man-Machine Interface).

USSD codes are a communication protocol that work across devices and create a real-time connection to information your carrier has about your account. Not every carrier or platform uses the same codes, especially globally, so these might not work everywhere. Also, they’re meant to be obscure, so I’ve opted not to list codes focused on diagnostic tools and pulling up technical information about your phone. What follows are some of the most useful hidden features you can pull up with a phone code.

Dial #225#, #225, or *225# to check your current bill

Who needs a carrier app when you have your dialer

Using a phone code, it’s possible to access the information your carrier has on the balance of your current phone bill. You can still find this information through your carrier’s app or website, but as a quick way to check your bill, it’s handy. On an iPhone or Android phone in the US, you can dial #225# on T-Mobile to check your bill, or #225 on Verizon, or *225# on AT&T.

Dial #932#, #3282, or *3282# to check your data

All that video streaming costs money, so stay on top of it

If you’re less interested in your bill and more interested in the amount of data you’ve used, there’s a code for checking that, too. The cost of data on your plan is often much harder to manage than minutes or texts. By dialing one of these codes on an iPhone or Android phone you’ll receive a text with your current data usage. You can dial #932# on T-Mobile, #3282 on Verizon, or *3282# on AT&T.

Dial *729, #768, or 611 to pay your phone bill

It still might be easier to pay online

If you need to pay your phone bill, there is a way to do it over the phone, just by dialing a specific phone code. Carriers want you to pay, and try to make it as easy as possible. There are plenty of ways to do it, and likely faster than you can do it over the phone, but if you own an iPhone or an Android phone, you can dial *729 on T-Mobile and #768 on Verizon. AT&T doesn’t offer a phone code, but you can dial 611 or call +1 (800) 331-0500 to pay.

Dial *#21# or *#67# to check call forwarding

Figure out where your phone calls are being routed

Call forwarding is a convenient way to temporarily direct your calls to a different number. You could forward your work calls to your personal phone while you’re running an errand, for example. You can use a phone code to quickly check if your phone has been set to forward calls to another number. You can dial *#67# to check the number that calls are sent to while your phone is busy or *#21# to see where all calls are being forwarded to.

If you receive an error message from your carrier, it’s likely because your plan or your software doesn’t support call forwarding. On iPhones, you can set up call forwarding in the Settings app, under the Phone section. On the Pixel (and most Android phones) you have to head to the Settings section of the Phone app, under Calling Accounts.

Dial *21 [phone number]# to forward calls

If you have a number in mind, you can start forwarding in your phone app

It’s likely easier to set up call forwarding in your smartphone’s Phone app or Settings app, where you typically have granular control over where calls are forwarded and when. But if you’re looking for a shortcut, there is a code for it. You can dial *21[phone number]# to start forwarding your calls to a specific phone number, by replacing “[phone number]” with the number you want to forward calls to. Doing this won’t eliminate your ability to make adjustments in Settings or the Phone app, so don’t be afraid that you can’t undo your decision to forward your calls.

Dial *#43# to see if call waiting is on

You should know what happens if someone calls when your line is busy

Call waiting lets you know if you’re receiving an incoming call while you’re already talking to someone on the phone. Most phones, in my experience, have call waiting enabled by default, but you can check for yourself using this phone code. Just dial *#43# to check. If it is disabled, you can enable call waiting in the Settings app on the iPhone or in the Phone app on most Android phones.

Dial *67 to hide your phone number

You, too, can appear as “Private” for a call

Having your phone number listed as “Private” protects you from people seeing your caller ID when you call them. Even if your phone number is public, though, there’s a phone code that lets you temporarily hide it for a call. It’s a great option if you’re calling a business or just another person you’ve never called before. To set it up, just dial #67 before the phone number you’re calling to hide your call, regardless of what carrier you’re on or phone you’re using.

Dial *2767#3855# to factory reset your Android phone

Don’t do this unless you absolutely want to erase your phone

Most of the time, factory resetting your phone to fix a problem or resell it requires digging through your Settings app. On Android, you do have another option, if you want to use a phone code. If you dial *2767#3855#, your phone will factory reset without warning or extra confirmation. I don’t have any screenshots of this because I don’t want to reset my own phone, but the option is there if you want to try it.

Your smartphone is still a telephone

It’s easy to forget what these things were originally for

When you consider all the different ways that smartphones can be used — as wallets, cameras, and computers, just to name a few — it’s easy to forget that, at their most basic, they’re telephones. Phone codes are a good reminder of smartphones’ inherent nature. They’re a very telephone-like solution to the problem of managing your cell service remotely, and importantly, they’re available for anyone to try. They might be more common at a carrier store at this point, but they’re still neat to know if you really want ownership over the ins and outs of your phone.

If you’re interested in other ways you can use more of your phone, Pocket-lint has guides on cleaning up Android, and tweaking iOS to make it more efficient. Both are worth checking out, because there are likely plenty of great features on your phone that you’re not even using.