Refuse to pay Service Provider

Gems is sending me from pillar to post about an outstanding Dr's payment. Every time I call they promise to fix the problem but they don't. Now I can't go for my post birth check up because of this outstanding payment. They claim the Dr claimed twice in 9 months all they do is give me references for calls and wait until I call again. I am so tired I need this matter sorted asap it's so frustrating. I spoke to Xolani he claim he can't see any outstanding amount from his side, but the Dr is still not paid