As a provider, if my phone # is posted on my showcase, website or any reviews, you may call me. But I don't post my # anywhere, so email either via eccie, my email address (if it's on my showcase, website or any reviews), or via p411 is preferrable.
Clients should not give out a provider's phone # if it isn't public information already. Email the provider. If she hasn't gotten back to you within a few hours, then let the client know she hasn't gotten back with you, and see if he would like to call or text her.
If you need any help or have any questions, feel free to ask.