Very Unhappy with dental whitening

I've put this in the other forum as well, hope its Ok.

I paid £400 for teeth Whitening, well actually £500 including a Philips Sonicare (which I love and thoroughly recommend). I didn't think to ask about a money back guarantee or anything. Guess I assumed I would get white teeth as I was paying to get white teeth.
When the treatment was done I kicked up a stink because I was unhappy with the results. He gave me another couple of sessions, and still I was unhappy with the results.
He then said "You can't guarantee it will work". Well there was no mention of that as he took my money.
Anyway as I left he gave me the trays, and I've never been back
A couple of years on, I'll give the Opalescence PF 20% x12, a go, at least I have my custom trays.

So please take care and ask for some kind of assurance or guarantee before you pay for expensive treatment.

Cheers from Eastern England