They have attempted this same thing with us. They will initially try to charge you£5.99 on the phone and say that they will not charge you anything else until they have achieved a reduction. On the phone call they will say that their only charge is that £5.99 plus a percentage of the reduction achieved. In practice, they use the £5.99 as confirmation of your instruction for them to act on your behalf for a fixed fee and will in a few days take a further more substantial amount from your card. It is as if by paying the £5.99 you are agreeing to pay them whatever the fixed fee is in their terms and conditions, which are only sent to you after you make that initial payment. I think these same people used to be hammer properties which were notorious for this and so they have changed their name. It seems they have paid for a few fake trustpilot reviews.