I have made up the sentence below.
(1a) I was cheated five times when I shopped at ABC.
My non-native speaking friends found two mistakes in my sentence. Their revised sentence is given below.
(1b) I have been cheated five times when I was shopping at ABC.
What confuses me in my friends' sentence is the use of the present perfect "have been cheated". The fact that the store cheated me happened in the past when I shopped there. The present perfect makes the sentence sound like I am still being cheated up to the present moment.
I also don't understand why "was shopping" is correct. The past continuous tense only works for an event that was happening at a particular time period, but for something that happened multiple times in the past.
Thank you very much for your help and time.