I'm not a ATT customer, first time iphone user, planning to use att for 15 days and get the credit and move to t-mobile network.

QQ s:
While purchasing the phone, should I choose the $45 monthly option?
I notice activation fee of $15 - is there a way to avoid it?
I read I can unlock as non att customer before switching on the phone, what are the steps I should follow after requesting unlock from the att unlock website - could not find this details anywhere.

Appreciate your time.