Slowing ppl down a day after taking their money

Im so shocked at rain service provider. After minths of 0.02mbps speed., eventually i get. Call back 3 months later. I get told all sorts of lies. I told them i was gonna block my debit orders.... And in 3 hours my speed went up to 16mbps.now 2 weeks later, literally the day after my debit otdee goes off....... My speed went back down to 0.02mbps and now they dnt reply to my calls. Anyone reading this.... Plz plz plz can you advise on me on hiw to take this further.???!!! I have now lost thousands in income and in the verge of loosing my job while these guys walk to the bank laughing. The service is absolutely appalling. And now, again, i wont hear from them for three months. And dnt even get me started in the staff member that told me its not his problem and i must sort it out.?!?! Thats what i get told. Not happy at all