Some dealers can be safe with you, others pretend to be safe to give you a flase sense of security, this way it makes you feel better and he is then able to do whatever the fuck he likes with your bud.

I guess the only way to get safe is to show your not a pushover, if you ring him and he doesn't answer don't keep ringing, it makes you seem desperate and easier for him to mess you about.

Also don't kep buying small amounts, and don't buy off the same guy more than once in the same week, that makes you seem more desperte and make him think that he is the only contact you have.