Furthermore, if you are required to answer the phone you are not resting. Period full stop. This is supported by numerous FAA legal opinions and your operator is in serious noncompliance. If this is a dirtbag operation (and aren't they all), your best bet to bring them into compliance and still preserve your job is to call and report them via the FAA Safety Hotline. Right now. 1-866-TELL-FAA. If you try to argue with the company directly you will probably be given the runaround and then when you end up reporting them, your boss will know it was you, and you can expect retribution.
http://www.nata.aero/data/files/abj/...ations_abj.pdf
"the FAA has said that for a “rest period” to be legal it must be: 1) continuous, 2) determined prospectively (i.e. known in advance) and 3) free from all restraint from the certiicate holder, including freedom from work or freedom from the present responsibility for work should the occasion arise."