cancel trade agreement

Go to Diplomacy screen, look for the country you need, then select another relation in the Your Relation column.

Thanks. I've done that, but it doesn't appear to change the relation. Does that also work to stop hostilities with a non player country, choosing peace? I've tried that as well, but it didn't seem to work. Thanks for the advice

You can still see his country, until he cancels his Share Map to you (see Their Relation column). You can also make peace with another player through this screen, but it will be, same as with Share Map, unilateral: you'll be at peace with him, but he will be at war with you. In this situation, the following can happen:

- he changes his relation to you to Peace - you'll have Peace - Peace between you

- he attacks you - that is not considered breaking peace - and you'll be at war with him again