computer speed

Cox internet speed is getting slower and slower.  It is not much better than dial-up.  When I first started with cox it was very fast.  Then you offered high speed ( which on my bill says that I have).  I inquired about it and was told I cannot get that.  I live in the wrong place. So, why has my internet speed gotten slower?  Is it so I will upgrade?  Well, I cannot. My email and anything to do with Cox is slow.

Thank you.