If you've been reaching out to them, sending them DMs, and they haven't responded, there's not much you can do. You have the choice of either letting their sponsorship proceed, or cancelling it and returning their payment. I would just let their sponsorship proceed since exposure is probably their primary goal, but you may want to err on the side of caution. When does the epoch they've sponsored begin?
I've been trying trying to contact nostr:nprofile1qqsfpncy8ps7tddfjukt0dff5ka8rvs46mg7x9x8f824ymkpx0cakucpz3mhxue69uhhyetvv9ujuerpd46hxtnfduqs6amnwvaz7tmwdaejumr0dsq32amnwvaz7tmjv4kxz7fwd4hhxarj9ec82cs4mg6se about their sponsorship because it seems they sponsored under the pretense the OpenSats donation was still going. It was probably my fault since I didn't update the UI at the same time we made the decision to put the donations on hold while we bootstrap the user base. So now trying to figure out what to do, but they haven't responded 😅
Discussion
It's the current epoch
Oh, then you don't have a choice. You have to just let it ride. When you finally get in touch with him, explain the miscommunication and maybe be prepared to make a one-time donation to OpenSats if he's upset about it. It will be a small price to pay to ensure satisfaction and future relations with him, and others.