I have found that when you have had contact with a civ and trade with them, you continue to have the trade when you lose contact with them. Is this correct?

It would seem to me that if England is trading cattle to the Mali for gems, they should never lose contact for as long as the trade continues.

Thoughts?

I have found that when you have had contact with a civ and trade with them, you continue to have the trade when you lose contact with them. Is this correct?

Yes.

http://forums.civfanatics.com/showpost.php?p=5143300&postcount=37

How do you cancel the trade, then?