Threatening Legal Action For A Paid Up Contract

My partner had a planet fitness contract, which he cancelled in April 2014. He paid the cancellation fee 17 April 2014, he was given bank details and a reference number via email. He received a confirmation email confirming receipt of payment & that his membership was cancelled. Yesterday 22 July 2015, almost 18 months later he gets a text message threatening legal action if he does not pay his gym fees. No contact numbers on text message, After an hour of phoning around we get hold of the right number and the person requests a copy of the cancellation email to be sent to her as she can't trace the ref no. We send it to her and hear nothing. I phone today. The person who I speak to today says the reference number I gave him, the reference we used for payment and cancellation belongs to someone else with the surname Luleka not my partners surname or anything close to his name. I ask to speak to a manager and just get put on hold forever, I phone back and ask for a person in charge. You can hear people talking in the background but no one speaks to me me on the phone. Beside the bad attitude and incompetence I suspect ***** happening at Planet Fitness. The ref no given was on email