Not informed & Bad Service

I am the proud owner of a Pajero GLS LWB. This is my third Mitsubishi and most probably my last. I took my vehicle to the agents Union Motors in Nelspruit for the final service under the service plan. This is the 100 000km service. My cars km reading is 100142. They declined the service because the rule of Mercedes Benz is that if a vehicle is even 1km over the 100 000km service, it will not be serviced under the plan. (1). I did not buy a Mercedes. (2). It was never communicated to me. Why don't they put a notice up in their fancy reception to inform customers of their rule? This is ridicules, and a very bad reflection on this brand. I have been servicing my vehicle religiously but obviously this is the end to my service record from the agents because I will surely not go back to Union Motors and will be looking at a different brand of vehicle in the future.