Mobicred's Lack of Professionalism Just Ruined My Credit Record!

Literally the most unprofessional and childish credit company ever! For almost 24 months now I have been paying all my accounts on time, just for this ****ty company to ruin it over a technicality! They claim I did not pay for December, but it was them that did not deduct the amount via debit order as was agreed (I had the money in my account the whole time), NOR DID THEY NOTIFY ME THAT IT DIDNT GO THROUGH OR ANYTHING LIKE THAT, but then immediately hand me over to lawyers (This is the first month by the way!). Now my credit score has gone down by 15 points and my report shows that I have missed a payment in the last 24 months (which cannot just be remedied!)