member ship not cancelled as promised

Planet fitness! My daughter who is 16 had a membership with you. Later on my son who is 18 decided to join the gym. I then decided that when he signs up for his, he requests your consultant to cancel my daughter's so that she can join under her brother as he is 18. Your consultant agreed and promised they cancelled her member ship as she now falls under her brother's To my surprise she now goes to the gym after a few month to be told she owes an an amount of R1800 and at the gym they are refusing to cancel her's saying they need to investigate. Please get this mess sorted out. You may send me an email to get their details. I won't call your customer service I don't want to run around for this