Maintenance plan

My maintenance plan was for 120000km. At 117000km we phone to find out about booking and was told by dealer we are still allowed to go to 120500km and be covered. At 120252 we booked. The service was not honoured. Wanted to Charge me R10500.00 for a B service. R4500.00 for seat belt holder faulty giving alarm on dash. The Radio that they also are aware of will not work the cd player. They said will remove and send for repairs also not covered. All was know by their technician before the 120000km was due. Now nothing is honoured. Been with John Williams formore than 10 years and had all my merc serviced by them. Now this.