Bought vouchers before price increase and split of services

I bought a few vouchers for microneedeling… At the time it was done based on the prices given on their website. When I used the voucher for the treatment I paid for , they want me to pay a difference , more than the value of the original payment made … There new prices shows now a split in the treatment that I got , therefore I need to pay the new price… You got my money for 6 vouchers … up to 2027… Meaning if I want a facial microneedeling… the current value will not be for my whole face and décolletage, but only for my neck …

Please advise …