There should be no problems with using batteries from other manufacturers. If you get batteries with a higher mAh rating they should last longer when fully charged.
as long as they fit,yes.generally not recommende to use significantly higher capacity due to charging limitations of phone base unit,but up to 8oo mAh would be OK
There should be no problems with using batteries from other manufacturers. If you get batteries with a higher mAh rating they should last longer when fully charged.