While the circumstances likely are much different, in the US it's usually cheaper for packages over an ounce or two to use a "parcel delivery" service like UPS or FedEx, although there are cases where the postal (USPS) service is competitive.

Our experience has been that UPS is generally a bit cheaper for large packages (> 10 lb or so) and when "ground rate" is acceptable, with FedEx getting our business (usually) when a fast delivery is needed. Your mileage may vary, of course.

(I can't remember the last time one of the publishers we work with sent us manuscript materials via USPS.)

Most such services, at least in advertising here, represent themselves as being "international" in scope, so there should be services available in your area(?). They should have websites where you could check on what services are available quite easily, if they are in fact working your part of the world.

John