QVC sends warning letters before they take this step. At a 70%rate, you were costing QVC money -- costs which got passed along to other shoppers. QVC is not alone in this practice. HSN does it. Even brick and mortar stores are tracking returns and turning away serial returners.
Unfortunately, it appears that QVC was not a good fit for you (no pun intended), and honestly, if you found yourself returning such a large percentage of purchases, why would you want to continue shopping here?