Hello KiHi10,
It sounds like you need to unblock a number, and we'd love to help.
Just to confirm, what steps did you take to block that number previously? Did you use the steps outlined on the following page, did you use a third-party application, or something else? Block phone numbers, contacts, and emails on your iPhone, iPad, or iPod touch
If you used the steps in the above link to block that number, and the number is not showing in your Blocked Contacts list, it sounds like the number is not currently blocked.
Are you viewing the Blocked Contacts list by going to Settings > Phone > Blocked Contacts? If so, the list of blocked numbers should appear there. "To unblock a phone number, contact, or email address, swipe left over the entry, then tap Unblock."
If you previoulsy enabled "Silence Unknown Callers" and you'd like to adjust that feature or turn it off, please check out this link: Detect and block spam phone calls
Thanks!