Maintenance plan confusion

On 9 April 2016 I bought a new Nissan X Trail 2.0 with a 5 year maintenance plan. This vehicle was serviced annually at DTM George. In April this year I called for an appointment for the last service on the maintenance plan. I got an appointment for 30 April and on my handing in my vehicle this morning I was told that the maintenance plan expired at the end of March? This was never pointed out to me beforehand and that, subsequently according to the above, the vehicle then had to be serviced during March. What makes this more intriguing is that in 2020 I could only get an appointment in May of that year. This whole matter is difficult to comprehend and hopefully Nissan South Africa can reconsider this whole issue sympathetically and do my last service according to the 5 year maintenance plan as I really do not think this evolved as a deliberate action or oversight from my side.