Who I have the same questioned this topic

My mom has a new iphone 6 and we live in a very rural area. She had a tracfone before this and didn't  have any problems, but her new phone won't make calls out of the same areas. Instead of the call going through in extended service areas the line never rings or it gives the message "You are roaming to call your mobile carrier or any other number purchase a calling pin by pressing 1 now" 

Ive tried *228 which helped my phone but wouldnt go through for hers. 

Ive already had a couple people try to help who uad never heard of the American roaming pin. I dont want us to go back to tracfones 😕 what can i do?