Slow speeds, lots of complaining and still no help

For months I have been complaining about slow speeds, they have changed all my hardware, they have upgraded the tower but my problem is not resolved. They keep telling me nothing wrong with speeds but when someone actually wants to make an effort they get it sorted, the problem is it only last for a day or 2 and then I am back to slow speeds, I have asked for credit on my account as I have paid up for few months ahead. No credit either. Amobia service is extremely bad. When I started using them they used to be extremely helpful Seems as they grow they just dont have the drive to keep customers happy.