Supersonic very bad service

When i joined Supersonic i had very good service from them but only lasted for a month.I had an 50 up 50 down speed all went well as soon as i upgraded to 100 up and 100 down my speed was lower than 50 i have been phoning them several times nothing has been done to my complaints and they will phone me back its been 2 week now and nobody phones me back.Every time when i phone them they say they have locked the problem on the system and will come back to me.Dont waste your time to go to Supersonic im done with them.