Overcharged for purchase on EBAY?

I bought a RADO watch on ebay for $340USD which summed up to be $395 CAD with shipping. I received the item today and its GREAT! I love it. I used my mother's credit card to pay for it. My mom was just looking at her credit card statement for last month and there is an online charge of over $900 on her statement. On top of that, they have credited $111 out of that $900 back to her. I am really confused. Was I over charged? I do not want to return the item because it is EXACTLY what I wanted but what can I do about this over charge? I used a president choice master card and used paypal. How do I contact paypal? Please any advice?