I've heard your guarantee offers quite a bit. When you say I guarantee you X days or you don't pay, how does the deal actually go? Do you generate and book a lead yourself by calling without charging anything up front until day X? Or do they get charged per booked appointment? Or do they pay up front and get a full refund if you don't achieve results in however many days?
I use a guarantee very commonly in cold email and other marketing methods — I'll guarantee X result in Y time or you don't pay. It's not exactly true if you take it super literally, since at some point in time they will have paid, but the framing is short and fits nicely above the fold of the copy. When somebody actually gets on the call, I clarify it's a money-back guarantee: if by the time I said I'd achieve the results I haven't, they end up in the same state they started in — the state where they didn't pay. I haven't had many problems with this, but I'm also experienced at explaining the mechanics — I've heard of situations where less experienced people run a similar offer, get on a call, the prospect asks how it works, and they fumble the explanation ('well, you pay me and then later I give you your money back'), which doesn't match what the email implied. So it comes down to skill in framing it live: I'm happy to front-load the opportunity, get people on a call, showcase a ton of value, and let them arrive at trusting me based on my YouTube, Google presence, etc. — results may vary based on how well you can do that yourself. If you don't want to run the exact same offer, you can just change the language at the end from 'or you don't pay' to 'or I'll give you all your money back' — and nowadays I wouldn't even recommend a plain refund, I'd add something extra on top, like 'or I'll give you your money back and get you a night at your favorite steakhouse.' When you do that and actually mean it, it massively increases your top-of-funnel — maybe 300% more people through the door — and the cost is just a 5-10% refund rate plus a small bonus, which is nothing compared to the volume gained.