Retrieve old phone number

Hey there, I had Xfinity Mobile services and I had to cancel it on around January since I was going out of country and won’t be using my services outside there. And when I called Xfinity they said they’ll hold my number and I can activate it anytime later. So I came back from the trip around Feb 27 and and I called them to activate my line on the Feb 28th and they said it’s successful and I’ll see it within 24hours but it’s been a week and I still haven’t seen the number yet. And yet when I call the customer service they say the deadline is passed and my phone number is gone forever now. But it’s that person’s fault who didn’t do it properly when I called on the 28th. I had my number linked with many important things and I need it. This is unacceptable service that they gave.