CHASE VISA Chase United Milage Plus I canceled my card and they took away qualifying miles wilmington, Delaware

I have been a chase customer for years; not by choice but because they bought my old credit card company awhile back. I had a very bad experience with them 25 years ago and have tried to avoid doing business with them since them. Unfortunately I cannot always do that. I cancelled my travel card with them on Saturday and today I received a letter stating that the miles I have acquired with them will be suspended because I cancelled the card even if I pay my bill on time. I spoke with their customer service rep and he was very smug and discourteous when he told me that "yes, even though you pay your bill completely and on time....you will lose those miles since you cancelled the card."