If you are in any sort of relationship NEVER NEVER NEVER use your personal number and never ever from a smartphone. Even though I have nothing to fear in that respect, separate phone (smartphone only because I hate texting on a dumb phone) payg sim and apps not installed and wifi off. I don't contact SP's via Whatsapp, again it seems to release personal info in some way, profilepics and what not. Not 100% certain as I don't use it on my personal phone either.
Too late for the OP, he's now at the mercy of the guy he contacted as to whether or not he tries to ruin the OP's life. Hopefully he won't, but likely to be a laugh between him and his mates down the pub.
Hopefully anyone else who uses their personal phone will learn from this. Even if you have nothing to lose a punting sim makes sense, that way if you end up being in contact with a nutcase (thankfully not that common) who contacts randomly or after a failed booking gives you repeated abuse, it's easy to change your number and let any SP's you return to know that you have a new number. Much more of a pain in your real life.
A couple of SP's have my real number also as I was having problems with my punting phone but these were ladies that I had visited repeated times. If I was having problems with my punting phone trying to contact a new SP, it would be radio silence from me, with an apology once sorted I'm afraid. Not worth the risk.