Open the Phone app
Tap the menu or More options
Go to Settings
Tap Blocked numbers or Block list
Find the number you want to unblock
Tap Unblock or the remove icon
Confirm if prompted
If needed, check Contacts, Messages, or Call settings for blocked numbers
On iPhone, go to Settings
Tap Phone
Tap Blocked Contacts
Swipe left on the number
Tap Unblock
Try calling the number again after unblocking