Ryanair Vouchers name mistake

I bought my parents 2 vouchers totalling 100 euros. Thing is, I made them out to both the names, First name & First Name, Surname. Now I realise that the voucher must match the passport name.

I was in a hurry at the time buying these. Is there a way of making a name change on them? Bet they'll rip me off

I know to change a name on a booked flight its €100