Q: I just reset My iPhone 4s and now it won't get past the activation screen it says that the activation server is unavailable and it is constantly looking for cellular service what do I do

Did you try to restore your phone, using iTunes on your computer and a Wi-Fi connection?

Did you already check this article?

If you can't activate your iPhone - Apple Support

Has the software on your phone been modified in the past?

Did you deinstall the beta software as explained in this article?

About iOS beta software - Apple Support

Maybe also check this article:

Troubleshooting iOS 9.3 Update Problems

These articles may help as well:

How to Fix iPhone Activation Errors - Try These Methods

Use iTunes to restore your iOS device to factory settings - Apple Support

If this does not work, your issue might be hardware related and you should bet the phone tested by visiting an Apple Authorized Service Provider or Apple Store next to your place, and ask them to activate it for you.

Find an Apple Authorized Service Provider