if the airline gives me a full credit for my airfares, but my new fares are more expensive, can I claim for the extra cost?

If you have been given a full credit for your airfares, we consider this as you being fully compensated for your loss, so there is no cover for any additional costs when you rebook your flight at a later date. 

However, if your flight is cancelled due to a reason that is covered under your policy, and at that time you are able to reschedule your flight to another date, there is cover for the extra cost of the rescheduled flight.

Cover is subject to the policy terms, conditions, limits and exclusions in the Product Disclosure Statement (PDS).