Wrong prescription

I went to specs savers on campus square for an eye test sometime in August . Then , the Dr gave me a prescription and he said l should get a pair for specs l got them and had to pay R650 to top up the amount since there was a shortfall with what momentum pays . It was only after 2 weeks getting that new pair l started having terrible headaches and l couldn't see properly in that pair due to covid and my school work . I then decided to go after 1 month . Told the Guy my problem then he said because momentum only pays for a specific lenses power he had to give me the ones momentum paid for not the ones my eyes need . So l asked whats the way forward and he said l will have to pay another R947 to get my actual lenses prescription. Right now as a student l cant afford to get such amount and now it seem like its my fault and spec savers doesn't accept their mistake