I think I mentioned in the Q&A video that you need to use ToPhoneNumber() to create the phone number properly.
I recommend that you use an expression like
ToPhoneNumber(Append("tel:+003",Task.numero_celular))
to create the phone number for the Callback, and see if that works better.
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George Ganahl CCXP, GCP
Principal Technology Consultant
Genesys
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