You probably don't have selectable sidebands but you will have a BFO knob - the problem is getting that knob set right. To do that - tune to a broadcast band station that you know the exact frequency - or better still WWV or WWVH on 5,10 or 15MHz. Set your frequency to exactly 5.000MHz or whatever. Turn to SSB and you will/should hear a tone - turn the BFO control until the tone reduces the tone frequency to zero beat - turning the knob too far will bring back the tone increasing again. With the knob set to zero beat, put a small dot on the centre of the knob - nail polish works well in the groove. The voice announcement on WWV should be understandable. Leave the BFO knob alone and tune to the ham bands, you should find that the SSB voices are intelligable, if not a slight tweak of the BFO knob should bring them clear. I don't know what the tuning steps are on your G3, 0.1kHz would be good.