I think marketing over the phone is a very bad strategy these days, because let’s be honest no one wants their phone to ring every 5 minutes and someone wants to sell them something - it’s very irritating. Furthermore, if you are going to randomly sell a service that is crypto-related in this case, I believe that at least 50% of people at best will not know what you are talking about at all - of course it depends on which country it is.

Therefore, it would be wise to come into possession of a database of those already familiar with crypto, and then contact such people. As for the approach itself, it is not logical to start a conversation without saying "hello", but what I can recommend is that the tone in which you will start is very important, and it should be as optimistic and friendly as possible - it can often work because humans value it much more than talking to robots.

Also keep in mind that people appreciate if you first ask them how they are, do they have time to briefly present to them what you offer - be creative, but also keep in mind that some people just don't want to do any business over the phone or just have bad experiences.