I'm looking for advice from anyone who has been through something similar with iD Mobile or LCS.

I had an alleged outstanding balance of £70 that was eventually referred to debt collectors (LCS). 

After I made a formal complaint, iD Mobile agreed to credit the full £70, clearing the balance completely. However, they refuse to admit any fault in the charges even though I spoke with over 12 different representatives who told me my plan was cancelled and there was no balance upon cancellation. These people are liars, who will tell you anything to end the conversation.

The part I'm unhappy with is that they have also refused to remove the late payment/default markers from my credit file, saying they "accurately reflect the payment history" and therefore cannot be changed.

I would like to raise another complaint but the team is a joke. I have proof of being put on hold multiple tines for 20 minutes multiple times just for them to end the call.

They are sadly professional time wasters.