My startup has a pretty unique problem, advice would be great

Hey guys, long time lurker and love the community here.

A couple friends and I have been working on our startup, Negotiatus, for a number of months now. Some quick background on the company - we are a b2b company that negotiates on behalf of our clients to save them money. Also, since we are essentially a one-stop-shop for their purchasing needs, we save them time and offer analytics, etc. The important part is that we charge a commission based on only what we save our clients, so we are risk free.

The issue is that our pitch isn't going over well with potential clients, because we apparently we sound "too good to be true" and come across as spam, a scam, etc. We are trying to tell them that we save our clients hundreds or thousands a month, with no risk and no extra cost to them, so I can see where they are coming from.

My question is - how can we pitch to potential clients and outline all the benefits we give, without sounding too good to be true?

Appreciate the help!