How much time do you have left on the non-unlimited agreement? Perhaps waiting until all are clear of contract/agreements would be easier, depending on time left. You could continue month to month with unlimited and the other line could change plans at that point as well. Again, depends on how much time you have left. This would allow both lines to be separate as well. If you choose to do so now, obviously speaking with a rep in a corporate store or over the phone would be necessary, but be careful and make sure you understand what they are going to do and that they understand what you want to do. Mistakes happen when plans get changed, and sometimes it turns into an ordeal with unexpected or mis-communicated intentions.
