Each DID in DIDX come with a certain number of Free minutes?, After the Free Mins are used the after free mins charges start applying, these charges are also prepaid in DIDX and you must have TALK TIME in your account, in order to be able to receive calls after the free minutes are over.
In Toll Free Numbers each incoming call is charged, therefore you have 0 Free Mins ( most of the time) and you need to pay for the incoming call, This again is taken from your Talk Time Amount.
Talk Time is used for all your origination calls, as on DIDX there is NO termination.
To Add talk time, Click on Add Talk time in your account.
You can also watch video , which will show you how to add talk time.