We have T mobile for cell service and plan to do nothing but use phones just like we do in US. If your phone is unlocked, you can get an E sim before you leave Texas. Otherwise you can get an international plan via your carrier. Last resort, just keep your phone is airplane mode, with wifi turned on. Though you won’t be able to use it without wifi but you will not incur any data charges that way either.
If the meds aren’t cutting it, get checked. Most pain comes from swelling. I’ve had two done. After the first week, it’s all about reducing salt and elevating and icing.