We use Zoiper 5, we want to purchase a PRO license, but we don’t like one thing. Very often they don’t hear me, the interlocutor calls from a regular mobile phone, I hear him perfectly, he does not hear me. The problem does not always occur, sometimes you call back and everything is normal right away. It's not a headset, we tried different ones, and tried from different computers, everything is in order with the equipment. Is it because of a free license? Or can I make some settings?