Is this really how it works? I guess you have to go to court to find out, but I ...

Is this really how it works? I guess you have to go to court to find out, but I always thought of it this way:

If I have the same policy (support for 1 year) and I change the contract - the change will only take actual effect after 1 year.

I mean, I'm contractually bound today to provide support for 1 year from today, no? Am I just rambling, or does it make sense?