Want to change plan from paid monthly to annually.

I have seen all the other posts regarding this.  I go to "manage plan"  When I click it I get only one option - end plan.  I don't want to do that.  I have seen it say to try again in 24 hours.  I have tried over several days - no change.  I want to avoid the new price increase by paying once a year.  I don't see any other way to contact someone for help.  Help!