My vehicle's license plate has changed to a GLC 300D 25 and I need to establish a maintenance schedule. To keep track of my yearly mileage and other statistics, I use the Mercedes website. The results show a variety of options, including the one I need—a four-year plan with two motorhomes and four services—for £42 per month. I will be contacted by the dealership of my choice to finalise the plan details. When my local dealership entered my information and requested a four-year plan, the system said that only a three-year plan, costing £46 a month, was available. Please, someone, tell me why this might be the case.