how can I get the speed that I pay for?

have had tech's over here to resolve but they don't seem to be able to repair. told me that my modem was failing but googled it and found out cox switched to a 3.0 modem. so a year ago bought a 3.0 modem. Cox keeps upping their price and wants me to up my speed. I keep saying you don't give me the speed I pay for now. have run speed test off cox site due to the one on the cox site times out due to time out error.