How to restore cancelled phone number

Last week I cancelled my phone number which was in a family plan because the plan was to be broken. But that was a mistake, now I want to continue use this number, so how can I get this number back?  I'm not the holder of that family plan but I know the account number and pass code.

I've tried https://www.att.com/suspend but it didn't work.

I've called att and visit att store but some of them said it's impossible to get it back if it was intentionally cancelled by myself. Is it true?

My friend told me that instead of asking for a "restore operation", which is bad because the family plan would restart and I have to pay for that if the number is restored, I should ask the staff to open a new line but with this same number, is it feasible?