Hey @Brunogag! I hope you're doing well. 🙂
Both those providers you mentionned in your post are partners we use in the US. However, service can vary between them depending on your location in the US. Network outages are also a possibility which could explain your troubles using AT&T. This is why we try to have as many partners as possible in a given country to provide the best coverage to our customers while traveling.
I hope this helps.
