Question blu studio 5.3s search for service

hello, ive got a blu studio 5.3s that im on straight talk (att) with. every other day i have to go into network settings and search for service and i have either roam3g or roam2g and i always use the 3g because its a 3g phone. but if i dont do this every other day i cant receive text or send text and on top of that it wont call out either. im not sure what the issue is, its a new phone so im kinda lost at what it could be. im using the APN from straight talks website. any help would be awesome and thanks much.