A lot of wholesalers like the idea of paying with cash. If you can emphasise that you're wanting to pay in cash as an alternative to credit I found they seem more interested
Also, like what has already been mentioned, try explaining who you are and what your company does and if possible, give an idea of how many units you'll be ordering. They'll see that you're serious AND you'll know whether or not they'll be interested after you tell them how much you'll be ordering.
Above all, come across as polite and professional.