Iphone11 - Call failed

We have two iphone at home, Iphone 11 and Iphone 11 pro max under same carrier (Movistar) from Spain, but different SIM and different numbers.

Last thrusday when we tried to call family in Cuba as usual, but both phones all of a sudden started to show "call failed" every single time we dial a local number. We tried many different numbers, cellphone, home.. but "call falined" all the time.

I have called other relatives and friends overseas in the US and some other countries in South America from both Iphone, and every single call got through without a problem, but Cuba impossible. We even tested my iphone physical SIM into a Samsung and same calls to Cuba and rest of countries got through, showing it is not a problem with the SIM, roaming or the carrier.

I have talked to both customer services carrier Movistar and Apple.. we went through many different tests, even reset the Iphone11 pro max a couple of times through Itunes, but no results! international phone calls to Cuba show "Call Failed" all the time.

I don´t really know why this is happening.. but it is very weird because I haven´t read any comments around the internet regarding this or similar issues with "call failed" to particular countries. It all started a few days after I updated to IOs 13.5 No idea if this could be related.

I am planing to stop by an Apple center and see if any tech staff can handle this issue. In the mean time, any light would be highly appreciated.