I hate to be mean but!

For years I've had an Amazon Prime account which I use regularly. My family members know this and they'll ask me if they can order things on my account and I tell them yes, to get the faster service. Well, a few years ago my sister was ordering things for her son and she checked her bank statement and saw that she was being charged for my monthly Prime account. She quickly stopped using my account. Now, for the past year or so my daughter has been using my account to order things for her daughter (my granddaughter) and herself. She just hit me up to say that she too has been charged for my prime membership and was going to call the bank to dispute the charges.

I do not mind paying for my Amazon Prime membership as it is very handy to me. Some months I don't order anything but I still pay for the service. Now my sister and now my daughter have used it heavily in the past few years and they are getting the benefits of my account without having to pay for it. But when their cards are being charged then they want to complain. One of my other sisters asked to use my account which I gladly gave her my login info. I look at it this way. You using my account means you need to help me pay for it too. If a month or so goes by and I don't get charged for the service because I haven't ordered anything byt you get charged because you have ordered items and added your card info to my account then why would I complain? I guess they expect me to call Amazon and have them just charge my card. Nope, you are using it so you help pay for it.

Am I wrong?