HTC One - 3G reception problem

[aponn]

Hi, I have a HTC One 32GB Unlocked version. I'm using "Family Mobile" service works on T-Mobile network. It was working good in Washington State with 3G data or H speed (Family Mobile dont support 4G LTE) but after I moved to Arkansas, the 3G or HSPA connection is lost. All I'm getting is "E" signal. Couldn't able to figure out the reason?
I tried factory restore. But of no use. Could you please help on this?