Received Sprint roaming too much letter

[13ducati13]

Been roaming only now on my phone for over a year, finally received the letter from Sprint stating they will drop me if I don't change my usage. Not really sure what to do, in my area if I have the phone set to 'auto' it doesn't work at all in my house and in a 5 miles radius around my house.

Any modifications out there that will somehow increase the reception on my phone?

I'm running a stock rom.