AIS vs Dtac GPRS

I am using AIS GPRS for my internet connection, red AIS tower very close, so good signal. No good alternative for GPRS. Paying 500 baht for 250 hours a month.

The problem is that most of that 250 hours is waiting time, often, especially recently - last two months - the download speed is aroung 10 Kbps, where a much higher number (300) is technically possible.
It gets me very angry that AIS sells something they cannot deliver, but TIT.

My question : is anybody having experience with Dtac Gprs ? If so, is it ok for speed ? Or any other company that delivers GPRS ?