The provider made that up. Toll Free numbers are no different than DIDs. You should ONLY be paying for minutes used and a small monthly charge for the numbers in question. Normally a monthly fee is $1-$5 per number (toll free or not). If you have purchased an "unlimited inbound minutes" number, they may be as much as $10-$20 per month, but they will also have a limited number of calls at one time (usually one or two, max). So never purchase unlimited inbound minutes numbers.
The "extension" concept is purely fiction, they are apparently trying to sell you PBX functions to justify charging you an outrageous fee for something that has no actual cost for them. Change carriers.
That being said: If you are outside the US and there is only one carrier, you may just be screwed. LOL (sorry, but true)
When routing calls to an ingroup in Vicidial, the vicidial system ensures only one call goes to each agent at a time. Toll free is not different for inbound in Vicidial, it's still just an inbound call. Read the manual