Postby dudette » Mon Mar 20, 2017 9:34 am
The grace periods are usually for things like very minor and obvious spelling mistakes. I'd be extremely surprised if they'd allow you to change dates - you could just have changed your mind rather than made a mistake for all they know. Most flights list the booking conditions when you book and if you booked a non-changeable, non-refundable fare then it is just that - you can't change it. The reason the fares are so cheap is precisely because they're non-refundable. Flexible fares where you can change dates are much more expensive.
I don't think you'd have a leg to stand on when it came to making a complaint so I think you'll just have to write this one off and be more careful next time. I book flights a lot and I always check, double check, and triple check before I send payment for this very reason. I'd say your only possible grounds for complaint are that Last Minute didn't make the booking conditions clear on their website.
The Telegraph Travel section has a very helpful Q and A column for people with complaints against the travel industry and they maybe could help but having read it for years I think the answer is very likely that they can't! Sorry.