1010158000 / 101-015-8000 Reverse Phone Lookup

I am reporting this for someone else. I work as a receptionist for a mortgage company, and a women called me who was trying to get in touch with one of our loan officers. She dialed our 1800 number, and said a voice came on the line telling her to dial this 1015 phone number. She did dial it, and she didn't get anyone on the other end. She said the operator came on and said if you would like to make a call please hang up and dial again. So she hung up and then dialed me trying to reach our loan officer. I asked her to give me the number she was told to dial and I would research it to find out what this number is. She is afraid she is going to be charged a ridiculous charge for dialing this number. I'm not sure what else to say, she didn't have much information to give me. But I just wanted to report this as it seems very odd.