@Roni I don't know why CS told you that you couldn't return multiple items from multiple orders in one package. I do it all the time (yes I return a lot but I keep a lot as well) and have been doing it for years.
I do however make sure to put the invoice of each item within the plastic bag that the article of clothing (I mostly return clothes) came in.
In addition, I use QVC easy returns. I send them an email letting them know what I am returning. I say what the item is, the item's number as well as the order number....give as much information as possible to make things clear.
I ask for a refund by the original method of payment and have not had a problem doing this ever. Once I send the email, I will hear back anywhere from a couple of days to up to a week and a half depending on how busy they are.
ETA: I actually have five items of clothing that I plan on dropping off to be shipped on Tuesday. I have everything packed up and ready to go in one box. They are from different orders and I will send out the email to the Q on Monday letting them know the items will be on the way back to them.