Burger King has announced a series of changes to its restaurants and menu after collecting feedback from customers who called in earlier this year. The fast-food chain says the updates are a direct response to what diners told it they wanted, forming part of a wider effort to improve service and address common complaints.

Among the changes is a new "Whopper Guarantee", which promises customers a free burger if their order is prepared incorrectly. Burger King said it opened its phone lines specifically to gather honest feedback from customers, and the resulting adjustments are intended to address the concerns raised most frequently.