I purchased a Full Synthetic Oil Change from Valvoline Instant Oil Change voucher that...

I purchased a Full Synthetic Oil Change from Valvoline Instant Oil Change voucher that I redeemed yesterday afternoon. I paid $**.** for the Groupon, which was good for one Full Synthetic Oil Change (valued at $**.**). When I arrived and presented the voucher (both in printed voucher format and via the Groupon app), the merchant wasn't sure how to process the voucher, what the voucher was exactly good for, and how to properly input the voucher into their system. After several minutes, the management team figured out how to input the voucher, but told me that the voucher was only good for the $**.** that I paid to Groupon, not the full oil change. I explained to them several times that the voucher was good for the full price of the oil change as it would not make sense for me to pay Groupon the $**.** for the voucher, only for Valvoline to take the exact same amount off of the oil change. After several minutes of respectful arguing with management, they told me that they could only take $**.** off of the service and that I would need to reach out to Groupon to resolve the dispute. **I'm hoping for at least a refund of the amount paid for this Groupon as I essentially was unable to use this as any sort of discount. The merchant only gave me credit for the amount paid for the Groupon, even though I purchased this Groupon less than one week ago and redeemed it yesterday due to the merchant being unable to fully comprehend what the voucher meant or what discount it reflected.**I have a receipt detailing the charges and discount applied that I'm happy to share via email or fax.**Thank you in advance and I look forward to your prompt response.