How to unblock blocked numbers on iPhone

To unblock numbers go to Settings > Phone > Blocked Contacts

Identify the number of the blocked contact you want to work with. Touch on it and slide to the left. You will see a red button labelled: Unblock. Touch on that and the number will disappear from the Blocked list.

Apple has further information about blocking numbers in Block phone numbers, contacts, and emails on your iPhone or iPad - Apple Support

To unblock a number or a contact

Settings > Phone > Blocked Contacts or Settings > Messages > Blocked Contacts.

Swipe right to left across the number, then tap Unblock

I don't have a quick fix for the other item that you mention. Things may improve though as you unblock contacts.

All at one time….. all

any help other than one by one?

I think you already know the answer to this one.