I do reservations for a small B&B and get paid per reservation I make. What is a fair amount to charge when it comes to my personal cell phone usage? I'm using my minutes to take these reservation calls and make myself available, but I don't know what or how to charge my employer. Any advice would be useful!! Thank you!

So you're a freelancer? if so then you can charge whatever your carrier charges plus some percentage, but whatever you do you need to make sure they agree on it, you don't want to create a situation over some phone calls, besides, leaving it for them to find out, like if you send them an invoice and include the phone call charge without notifying them and leaving it to chance, this may cause them to raise their guards and be more careful while dealing with you, better to be straight forward from the beginning.

But from a business owner's point of view, they may debate that they shouldn't pay for it because they don't care if you made a phone call or went to the customer yourself, all they would bother to pay for is the commission for your reservation, that's why you should agree with them from the beginning on this and if they don't want to pay for it then you could try a cheaper way to call your customers, I hear Skype is offering cheap rates on landline calls, anyway I leave it to for you to decide, just don't make a big deal of this.