MBD *********** attorneys with continues threats

If closed my Virgin Active account more than 2 years back. Since then no sms's, emails or calls to say that theres an outstanding amount. Since beginning of February 2019 if been continues harassed by MBD stating I owe them R 1500.00 for outstanding Virgin Active fees. I've requested for 2 weeks for a formal letter to state the amount thats outstanding. I received an email that looks like its been drawn up by a 12 year old. Since then ive tried to phone to speak to a manager or supervisor or some one competent enough to explain to me how this is possible. The only response that i've received is to say that it was only handed over in June 2018 and that I have to understand that they are busy so they cant phone you as soon as they receive it.

Can you please advise me on what action to take. Ive been constantly harassed by MBD and no proof to show that I owe them money except for a letter drawn up by a child. Ive been give a incredible discount which is F@$k#% up as I dont believe I owe them anything. This company is busy influencing my work and threatening me with sms's which states legal action will be taken.

I can promise you I wont leave it at that.