Hello & Welcome to Just Answer,
I'm Greg and will do my best to assist with this issue today.
Sorry to hear of any issue you are having with your phones.
To help you with this issue:
Let me say that writers of the documentation for these phone system did include how to unblock a number, BUT the instructions are NOT easy to find or sometimes interpret.
To help you with this issue, I have attached some ENHANCED instructions, about how to ERASE a number that is on the "block list".
NOTE: The attachment is an image, and you may have to click the link below to see that image.
Please take a look at those enhanced instructions and let me know if you can interpret them, or if you need a little more help with that.
Then TRY those steps and let me know if you can SUCCESSFULLY remove (erase) the number from the block list.
Thanks, ***** *****