Regus review: Leatherhead virtual services

Our company has held a contract with Regus Leatherhead for 13 years. Never once have we not paid our account or made any changes to our service. A few months ago, they claimed our direct debit failed and we owed 3 months' worth of invoices. We disputed that our direct debit had failed as we have another account with Regus Manchester and the same direct debit is used for them and had continued to go through just fine (this is also the same direct debit that has been used to pay our invoices per Regus' requirements for the last 13 years). They locked our account and said we needed to pay the full amount before our account would be unlocked and we could reinstate our direct debit. We did this, but they neglected to unlock the account. 4 days later, another bill was issued. Because they had not unlocked the account, I was told we would have to pay this manually as well before the account could be unlocked. I complained as this was their failing, not ours. They begged us to just pay this time and they would sort it out, so we did. When they did unlock the account, they realised that there was an issue with their system, and while we had a direct debit set up, their system would not let us select it. I was assured this would be resolved, but 2 months later, nothing had changed. In the meantime, they had the nerve to slap us with a payment method deposit bill for apparently not having a direct debit set up! We also realised that they had been wrongly charging us for an additional mail service when no agreement for this was in place. When I pointed this out, they tried to add the service back into the account to justify the charges. I again complained and accused them of underhanded practices. They said they would remove the service and credit the amounts we had paid. To date, only 2 of the 3 credits have come through. We have complained over and over again about the payment issue and had to chase they every step of the way. We said that if they couldn't sort it out, we would cancel our agreement and would expect them to waive the remaining months as the issues with our account were totally on their end. We were assured that it would be resolved and that someone would get back to us. Of course, no one has gotten back to me so we have cancelled and are now being sent threatening letters about debt collection and legal action. They have not responded to my emails.