Unfortunately, 'post-mortem', it's hard to do anything now.

In general, with any service, it's sensible advice to try it with smaller amounts first (that you're comfortable to lose in the worst case), before attempting a larger amount. This no guarantee for success though, since some services do increase e.g. KYC requirements with the amount of money in question.

Another piece of advice would be to use non-custodial services, such as Boltz for instant-exchanging, which use chain swaps instead of physically handing over control of your coins to a third party and then hoping they don't rip you off. This means in the case of Boltz, they basically can't get the currency you send, without sending you the exchange currency. Unfortunately, as far as I know Monero can't do that yet. This is also possible for going on-chain <=> Lightning, in that case it's called Submarine Swap.

For exchanging Monero and BTC in particular, I'd probably recommend Bisq. It has no notion of taint and it's purely P2P-based and decentralized.

Finally, if I really needed to use a centralized service, I'd use something more trusted, with known working customer support and all that.

LoyceV already mentioned my blacklist topic and I just added Openchange.cash; unfortunately it's hard and I wouldn't attempt to create a 'whitelist', since it's impossible for me to guarantee that a service is trusted and reliable.