final warning

last year at around June I was at Maponya Mall with my friend and we come across this guy from gym company and asked us to join the gym and we told him that we cant because we do have gym at work, then he asked us to give him our names, cell numbers and ID numbers because his new and they want to know how many people he told to them then we did that after he asked us to go with him to look at the gym and we did. Now Monday I received a letter telling me that I have outstanding amount of R8647.00 and I have to pay it before 20 days, I have tried calling them they not answering and I have email their manager she doesn't respond and now she's not answering her cell phone