Vodacom charges extra for a prepaid service on a contract

With the use Caller ID on a prepaid vodacom sim it is a free service to use, but when you change or take out a contract at vodacom they do not tell you that you will be charged an extra R10.00/month to have the service that you always had on prepaid. What difference is there between a prepaid and a contract sim, this is clearly vodacoms way to get more money out of you so think carefully before you get a vodacom contract as nobody tells you about these hidden costs. You would have though vodacom would have been nicer to people who have a 24 month commitment to them over someone that does not pay them at a regular interval.