is it the best to do an encrypted back up on iTunes ?

You seem to have 2 unrelated questions.

If you are backing up to iTunes you should encrypt the backup. If you don't sensitive info like passwords and health data will not be included in the backup. But when you enter the passcode write it down; you will not be able to restore the backup without it, and there is no way to recover it.

What happens when you try to answer phone calls? Does the phone ring more than once, or only once? If it rings only once you have call forwarding enabled. You need to disable it if you want to receive calls on the phone.

If there are other questions or issues post back with more details.

You have 2 questions?

1. Your question title: Yes the encrypted backup contain more data (example health), but if you forget the password, you will not be able to restore from it, read here: About encrypted backups in iTunes - Apple Support
2. Cell connection is your carrier service, talk to them since you are paying for it.

You're welcome.