My iPhone thinks I'm some else...

This really weird thing has been happening with my iPhone. It thinks I am one my friends in my Contacts. Last night, I made an online purchase and although I was billed for the transaction, (I paid with Apple Pay) the receipt was emailed to a friend. Another example is that on my Apple Watch, when I close my exercise rings for the day, I get a message (on the watch) that says "Well done ________________ "(friend's name). it's always the same friend. What do you think is going on and why is this happening? My iPhone is linked to my iCloud account. I have tried deleting that friend's contact details from my address book, but it made no difference. It has been happening for a while now, but I can't recall other specific examples at the moment.