Stop bullying the little people Virgin Active

In Jan 2017, I signed a 12 month contract for my 15 year old son with Virgin Active. He used the facilities for a max period of 3 months during the 12 months, yet I honoured my 12 month contract. I in fact paid for 14 months. After 14 months a stopped the debit order with the bank. In Sept 2018 I received a call from an Attorney firm stating my account was handed over due to non payment. I was very surprised as I honoured my contract. I went to the Virgin Active where my son was a member to enquire about this, and I was told that if I wanted to cancel the contract after 12 months, I have to cancel it in writing in month 11. This was conveniently not told me when I signed the contract. I then requested a copy of the contract as I never received a copy when I 1st signed it. I resigned from my work in Aug 2017 and my contact details changed. Apparently an email was sent in Nov 2017 and Feb 2018 advising me of fee change and the contract that was expiring. I never received this as my contact details changed. They also tried to phone me, but did not get hold of me due to a new cell number. I asked them why they did not cotact my son when they could not get hold of me as his contact details is also on the contract and I was told he is under 18 and he could not be contacted. I then asked them why they did not contact him to ask him to give me a message, and I was told again he is under age, which I think is nonsense as they did not have to give any information to him apart from asking him to ask me to get in contact with them. If I was told by the agent to give notice should I not wish to continue when I signed the contract, it woul not have been necessary to hand my account over as I would have given notice as my son wasted my money in the 1st place. They now refuse to reverse all the charges and said my account will remain with the Attorneys until fully paid. I do not see why I should be held liable for something I was not told when I signed the contract and if I honoured my contract and paid 2 months extra?