Just recently upgraded to Samsung Galaxy A5 2017 & as I've previously posted my new phone won't work with the app. Here's the thing tho' my previous HTC ONE (the very first one released) had no issues with the Three App & that one had been migrated from Vodafone to Three. Strange that a phone just about six months on the market isn't compatible with the app while an ancient HTC worked fine. Tech guy I spoke to some weeks ago said that they were working on it. Still not sorted yet tho'.
Brogan, thanks for the offer of help but I have been through this hoop several times to no avail. Each time I'm told that the problem is due to my phone being a non Three device. This is just a fob off by Three as it is well documented that the app doesn't always work on Thee supplied phones either. Three need to accept that the app isn't fit for purpose and sort it out.