BTDT. I was introduced to a really interesting and friendly woman who I really got along with. Then she started the sales pitch. No matter how many times I declined she persisted and sprung her presentation on me one day when I went over for a cuppa. So not cool with me and I told her I wasn't impressed. I've ignored her attempts to contact me ever since because I know she had a motive.

I'd be upfront from the begining and let them know that you are not, in any way interested. You don't need to provide reasons. You don 't have to explain yourself. I hope they respect your decision.