4G not working overseas

I guess it depends where you are in Spain, as different locations vary, but I roamed in both Mallorca and in the Canary Islands this year.  I found that Movistar was the network my phone preferred to connect to most of the time, but this signal varied between 3G and 4G…3G more often.  
I soon learned that Orange was a better option, with 4G the majority of the time.  
I turned my phone from automatic to manual and then chose Orange…so if it is available then try manually selecting it, or try some of the others.