Overbilling, bad customer service and total lack of communication

RCS/Edgars, since 25/09/2020 continue to ignore resolving overbillings and unjustified charges that go back to March 2019. Many e-mails and merry go round phone calls. I started to deduct these charges (as a Consumer Right) from my monthly payments and continue to receive letters of demand, threatening black listing and then get billed for these letters and reminder of payment sms and phone calls.