Mercede Benz Motor Plan - is it really a motor plan?

I took in my Mercedes C200 which is about 3-4 years old - to the dealership as the "Check break pads" warning light had come on. The car is on a full motorplan. I just got a call to say I will have to pay for the new break pads as the car has only done 15 000km since they were last changed and they are supposed to last 17500km. I drive my car to and from work about 10kms per day in total. The car has 32 000km in total after roughly 4 years. The cost of the new break pads is north of R12 000. I struggle to see how this is not covered by the motor plan. Clearly I must break very very badly on my 5km journey to and from work each day. A motor plan is a motor plan and when you buy a high end vehicle and you're told it has a 6 year motor plan - that's pretty much why you buy it for the piece of mind that you're all in irrespective of what happens. What will happen if the gear box goes will someone be accused of accelerating badly ? I quite like the Mercedes, but they've lost a customer for life.