Eyelash Answers

What happend is I had an eyelash perm & tint & i was not happy with the results as it did not work! so I informed them,a few days later & went back in & the supervisor present was not disposed to offer me more than 50% discount of another treatment, even though it did not work the first time & I would have at least expect them to do another treatment free of charge as it was less than a week & this is supposed to last 5-6weeks or so!
At first I was ok with this, however after thinking about this why should i pay again! & I even suggested 50% refund back to me then.
I wrote a complaint letter & the salon (not a cheap one!) still only offered me 50% discount & a £5 off voucher for another treatment as a gesture of goodwill!!!! (making me spend more money, as if!)
I feel this is very unfair & not good customer service at all, I have tried again to put my point across, but the supervisor was very rude & said there is nothing further they could do & that they do not offer refunds. Help!