I was in the queue to buy metro tickets today and a couple of tourists were having a hard time purchasing them. I wanted to explain them that the old one pound coins were removed from the circuit yesterday. I told them 'they have been removed' instead of 'they were removed'. I think I did a mistake because it is an event that is finished in the past but somehow it emphasize something in the present as because of that they can't us them. There is for me a grey area between those tenses and I would deeply appreciate help.