Useless accounts department

I recently cancelled with this company, when I say recently I mean back in April with the contract ending end of May. My acc was up to date but a few days before May ending they cut my line... I called to find out why and I was given some nonsensical reasoning like my acc was in arrears, I asked for them to prove this as I knew that it wasn’t possible, to which they failed then changed the excuse to that I cancelled. I agreed that I had cancelled but because I paid the full month’s premium I expected to have internet until then, so they reconnected me. Fast forward to August, I haven’t been a customer of theirs for the past two months, I get an invoice stating I owe them for February. I obviously dispute this and we have a back and forth with Jackie Jacobs that it’s impossible that I owe them a cent because they would’ve cut my line back then when I was a client if I had owed them for so long. I then send them proof that I made the payment and after that I never received a response nor an apology for their baseless accusation. That accounts department is a **** show if you ask me, they don’t know what they’re doing and it’s not the only occasion where I’ve had to help them do their jobs. If you want a headache then sign up with these clowns! Not forgetting how often they’re offline and you go a day without connection!