3 moms living at the same address?

I've been staying with my mom while waiting for my apartment and last week she asked me to help her manage her bills. I figured it was pretty straight forward - i'd get a stack of paper bills, go online and pay them off one by one. Shouldn't take longer than 1 hour max right? Not exactly. When I went to go pay off her phone bill, I had to enter my credit card details 3 times because she had 3 different phone lines at home. The phone company's systems treated the 3 numbers are 3 different customers, even though they were all linked to the same address. So here is my question for you information management buffs: what could the phone company have done differently to make it easier for me to pay off the monthly bill in one go?