Unstable Internet speed.

I recently switched from ATT DSL to Uverse. I never should have!.. I had great service now same computer no additional apps or programs and what took seconds now takes minutes to hours. One minute ai have good connection and 5 min later horrible. It seems to be ok for 10 minutes after I reset the modem then back to useless. I have the highest speed available for purchase and I would rather be on dial-up.. I have called customer service over 10 Times on this issue and have gotten nowhere. I have filed a formal complaint and still nothing. What can I do ????