I would be tempted to wait a week or two before calling. When changes are made to schedules or operating carrier it usually takes a week or so for Qatar to issue a customer service policy to permit their agents to recognise the change as an involuntary change, and provide a specific remedy. If you call before the policy is in place you just hit a brick wall as the customer service agents have no flexibility other than working within the fare rules and policy provided.

In this case I would expect Qatar to issue a policy to offer for customers now on an IB operated flight a move to a QR operated flight at no cost. They did a similar policy when one of the HEL flights was changed to being operated by AY, you can search for the threads in the forum for info