Help Slow 3G on samsung s2 on pageplus

[helpless85]

I have a Sprint Galaxy S2 that was flashed to Pageplus. the 3G is very slow. My pic messages take hours to receive or send and half of the time the message fails. I also have the same problem with sending group text. Please give me some instructions to resolve this problem. thanks.
I am so sick of going back to the store.