And if I change providers there are settings called "APN" settings that you change to get your data flowing again for the apps. This is not an offer to write what APN entries to use or how. That changes with the carrier but is documented widely.
I can see what some folk scream it's hard or complicated and have the change done at the carrier.
Something about your post worries me. You do backup your phone? I found iTunes to be good enough for me.
I have an Iphone 4S and am changing service provider.
I have never done this before with an Iphone, and believe it can be a nightmare
Any tips? I believe my sim card holds no data, and everything is on the phone.
Do I just change sim cards?