Warning: DO NOT put the phone in water. They told me I had to contact Sony for anything like that. Well I contacted Sony again and after taking some time they told me they could not help me due to contractual obligations between Sony and Bell that they couldn't work on any phones sold through Bell. They told me to contact Bell.
I hear you! I had a problem with my old Z1 (Bell model) and I too was ping-ponged back and forth from Sony to Bell. Apparently ALL Bell registered Xperia IMEI's have to be serviced by Bell, Sony won't accept RMAs for those units.
At the end of my ordeal, I gave up working with Bell and just bought an unlocked model.