Receiving call problems

[Muiris Pratt]

I use bluetooth to connect to my car, and don't turn it off when I exit my vehicle. I noticed my phone has been shooting calls straight to voicemail whenever I am not in my car. I also have internet calling activated to use my phone as a VOIP device. I also leave this on. Could either of these prevent my phone from ringing? Is my bluetooth trying to connect to my car and failing, putting my calls to voicemail, and/or is my phone trying to connect to my router and failing and also putting my calls to voicemail?
Thanks for any info!