Virgin active membership and affordability

My 19 year old son entered into an agreement with Virgin Active gym last year. He earns R2000 a month as an apprentice and the monthly membership fee is R600. I feel that he should not have entered into the contract but I also believe that Virgin Active should have checked affordability. He cannot afford this. I raised this issue with the head office and they said they can't engage with me, only with my son. On the issue of affordability they told him that they don't do a credit check. To cancel the contract obviously incurs quite a hefty penalty. This is not treating customers fairly and I will take further steps..