Internet Troubles

My wife and I became costumers of T Mobile in June. We also got internet service. As of today, August 12th, we have gotten a second gateway for internet since June. It still keeps lagging, and it still keeps going offline. What should we do? We have looked at reviews of the internet, and the internet reviews aren't very good. We plan on keeping our phone plan. It keeps disconnecting and throwing up error code WAN002. What should we do about our internet?