PAYING FOR A 20MB LINE AND ONLY GETTING 10MB SPEED

I phoned to tell you to fix my line, I upgraded, you are billing me but still I am only getting a 10mb speed. When are you going to sort this out. Today is the 12th, half a month has passed, I want a refund for the time that you are *****ing me. If I only get 10mb speed then I am only paying for a 10mb!!! Sort this out Now!!!!!