Why is the customer service so bad?

Why is it so hard for Xfinity to port a home number from another company to a phone on my plan? I have contacted customer service multiple times over the past month to get my elderly mother's home phone number ported to a phone she uses on my account. After roughly 4 days from the initial request, her phone was deactivated and no longer works. I have keep getting transferred to multiple CSRs during each call, each time having to validate my account and repeat the problem. Currently looking for another company to change my business to that will actually get things done.