Hi @DrDavidIsradeGlz, welcome to our community!
I have translated your question to English as this is an International forum, please post any replies in English and will be easier for me and other users to assist you.
To unblock a blocked number, open up the Phone application and tap the 3 dots in the top right corner > Settings > Block numbers and tap the little "x" next to the number you want to remove from the list.
I hope that answers your question! 
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