Left ear cup suddenly stoped working. HELP!

I have used the headphone for about 1 and a half year, so warranty is not an option and I don't live in north America (where I bought it from).

So the right ear cup where the controls are present works but the left ear cup doesn't. I tried plugging in the wire that came with still same problem. It's a Bluetooth headphone so there is no loose connection problem as there is no wire involved. The thing is that the charging port is on the left ear cup so I thought the band connection(from left ear cup to right) is loose or lost. But that's not the case as I plugged it in and it was charging, even the audio cable was working. I couldn't find any type of openings so I couldn't open the headphone to inspect. Can you guys suggest something. Thanks!