14 DAY TRIAL // Nokia Lumia 630 and 635 are the first smartphones on the market to ship with Windows Phone 8.1 operating system out of the box. This might be one of the reasons that these devices will be pretty popular among Windows Phone fans until new handsets are unveiled by Microsoft.
Anyway, it appears that some Nokia Lumia 630 owners report issues with the audio during incoming or outgoing calls.
The issues are highlighted by Polish blog site Windowsmania, which also claims that the cause of this problem may be the dual-SIM software embedded into Lumia 630.
Unfortunately, there's no way to fix this issue, so Nokia Lumia 630 owners will have to wait until Microsoft acknowledges the issue and delivers a fix.
However, a temporary workaround to solve the audio issue that seems to affect both the speaker and the microphone of the smartphone would be to switch the handset off, remove the battery and SIM cards.
Then insert the SIM cards in the corresponding slots, along with the battery and switch the phone on once again. In case this does not solve the issue, then you might need to reset the device to factory settings. Stay tuned for more updates on the matter.