There are several variables to consider, but to give a very vague and conservative estimate as a quick answer to a complex question...

Depending on your chosen bitrate, 10 hours of SIP calling would use approximately 1GB of data.

In terms of bandwidth, this is mostly determined by your chosen bitrate, but is increased slightly by the associated non-audio data that is sent alongside each stream. And remember a 2-way call has a stream in each direction. Therefore...

A 2-way 64kbit/s call will use approximately 150kbits per second.