When you take a car in for a service, you are not charged whilst you wait in reception, discussing your problem, if any. From the moment you phone a premium line you are charged at the premium rate applicable. Similar to the 0870 service whilst you are put on hold, due to 'all our agents are busy-please hold'.It is your telephone bill that is mounting up, not the support teams.
Personally, I like to buy local where possible. Nothing like going to the shop/store and having a face to face chat :o)