Apple Watch 24 Month Cycle is Apparently Actually a 26 or 27 Month Cycle

In December 2015 I obtained my Apple Watch with Discovery Vitality, and Discovery's welcome email to me indicated that evaluation for the watch woul start in January 2016, as December was already underway at the time. Each month's targets are taken into account when charging me for the watch on the 10th of the month following that (January penalties are charged on 10 February, etc.)

This means my 24 months of evaluation for the Watch would be for the months January 2016 to December 2017 - 24 months. The last penalty fee would then be levied on 10 January 2018 and the benefit would end.

Discovery is however claiming my benefit is only ending on 28 February 2018, and that I can't apply for the next watch until after this - which is 100% incorrect - unless the Watch benefit is 26 or 27 months and not 24 as advertised.

I want to get a new Watch now to have its benefit start just as the current one ends, but Discovery want to charge me an additional fee for that to be possible - which is not the way this agreement was advertised by Discovery.

Discovery never properly planned the upgrade process, and now are seemingly planning on overcharging me (or requiring more than the advertised excercise goals) for the Watch.

This is incorrect, and Discovery needs to review my query...