I have been using 64GB uSD since day one on mine and have no idea what the whole discussion is about. 64GB cards have been working on Android for a year at least and manufacturers only try to cover their backs in case of problems.
The whole is about file system used on the card. We used to have to use FAT32, now exFAT gets more and more support.
Why even start a thread like this if multiple threads have been created where people said they used 64GB?
Onr thing to remember:
NEVER TRUST CALL CENTRE/ CUSTOEMR SERVICE.
I used to call customer service for fun and ask a difficult question and then call back in 5 minutes, just to get to another person and get yet another answer. The third call meant another version of the answer.
People who work there are neither IT, nor Android experts and only use a script that tells them what to do in case of a specific problem. I have seen people working at an IT helpdesk for 2 years and when I told them to go to Device Manager, they did not know what that was. That just proves my point.
OT MaxDB, CD1, CD5, J5, GD96, ME45, T68i, X6, CX65, A925, E398, MPx200, X6-2, OT715, D600E, W810, M600i, BB8100, W880, N95-2, P1i, Ignito, W880, X1, MS1, MS2, TP851, XT910, GTab 10.1, SGS3, SGS4, SGNote 10.1, Nexus 7 II