My iPhone is banned from Snapchat and I just bought it

Contact Snapchat support. It's their ban, nothing to do with Apple, and only they can lift it.

You can try to explain the situation to them and see if they will unban the device for you.

https://help.snapchat.com/hc/en-us

If you can't return it and get your money back, you will have to live with the fact that you will never be able to use snapchat on that phone.

That's one of the pitfalls of buying a used phone.

It would appear you bought a used, stolen, or counterfeit iPhone. Once a phone is banned by Sanpchat there’s nothing you can do to remove the ban. Only Snapchat can do that and based on previous questions about this issue it’s almost impossible to get Snapchat to do so.

what do I do

Return the phone for a refund. You don't want that phone.

Read the section on social media banned devices in this link --> The All Too Common SAD Reality of Buying … - Apple Community

Lillymaygrether wrote:

How do I get Snapchat back on my iPhone after my mom deleted the Snapchat app and the App Store on my iPhone

It is impossible to delete the App Store app from an iPhone unless

• You live in the European Union, and have gone to the trouble to install an alternative App Store first.
• You have a jail-broken iPhone.

What seems more likely is that your mom is using Parental Controls to limit your ability to download apps from the App Store. In which case, you would need to convince her to let the Snapchat app back on your phone.

Lillymaygrether wrote:

How do I get Snapchat back on my iPhone after my mom deleted the Snapchat app and the App Store on my iPhone

Clearly your mom doesn't want you to use Snapchat on your iPhone. This has nothing to do with Apple, nor can anyone here help you bypass parental controls to defeat what your mom has put in place. I'm betting your mom bought you the phone and pays for it. You need to follow the direction your mom has put in place. I can assure you if my kid disobeyed me on their phone, they'd not only not have access to Snapchat, they'd have their phone taken away.

How do I get Snapchat back on my iPhone after my mom deleted the Snapchat app and the App Store on my iPhone

By talking to your Mom about it.