Seems to me the BB is referring to making VOIP calls over the internet using a WIFI connection. A lot of smart phones make this possible now and, if your son is a college or university student, he will find WIFI all over campus (unless he goes to Lakehead u). VOIP from a smart phone will not be the same quality as using the carrier's voice service, but when $$ are an issue (what student doesn't have $$ issues these days?) then it may be an acceptable trade-off, especially considering the elimination of LD.
I'm not familiar with the APPs for VOIP on a smartphone but am sure you will get help with a Google search of that. If your son has a data package on his BB9700 I think he should be good to go but stand to be corrected if Rogers perhaps blocks any internet options on the student plan.