a) consignments from each of them shall be forwarded charges paid by the consignor as far as the frontiers of the State in difficulty, but not beyond;
b) consignments to destinations in each of them shall be forwarded charges paid by the consignor as far as the frontiers of the State in difficulty, but not beyond;
c) consignments to or from the State in difficulty must not be made subject to any cash on delivery payment or disbursement, except up to specified amounts:
d) the consignor may not modify the contract of carriage as far as concerns the country of destination, pre-payment of charges and cash on delivery payments.