Can't use mic without headset?

Hi everyone,

I just bought a used Behold 2 off Ebay - the seller said it was in great shape, working condition - and it is, except for the fact that I can't use any of the voice functions or hear/speak during phone calls unless the headset is plugged in...

I can hear sound from the phone - i.e youtube videos and the start up sound of the phone, etc. - just not when in a phone call - also the speakerphone icon is grayed out and unable to be used...

I actually like this phone, but unfortunately, I need to be able to actually make phone calls with it too,

Can anyone help!?