lack of customer service

I bought a groupon voucher to service my car with BPF service centre. i bought the voucher in Nov 2015 if I'm not mistaken so was only able to book my car beginning of Jan 2016. when i got to BPF centre i was told there was a fee that i need to pay which was not stated on the voucher i therefore couldn't service my car. I than sent groupon an email requesting a refund as that was not within the rules of the voucher and my car is yet to be taken to service. it took groupon something like a week to respond, when they did the tel me of a 7days period has elapsed i explain that i wouldn't have known that i would be asked for more money had i known well off in time i would have requested for the refund a long time ago. the call centre ladies that helped me on 2 occasions that i called were very rude ref 320490 and ***7. when i asked to speak to their supervisor they were in a meeting or on a call on both occasions. anyways i still need the refund as my car still needs to go to service regardless of this whole mess and groupon credits will be of no use to me as i cannot pay with it.