one question, let's say if I send out a parcel and it normally takes 3 days to reach the recepient. What if I suddenly found out that the address I wrote on the parcel was wrong. Can I call up the pos office and request the parcel to be send back to me?

If this is possible, then I got another idea. If we had a deal and I need to send out the parcel via poslaju but we are doubtful of each others creditability,
is it possible that on day 1 I send out the parcel, then I let you know the tracking number that tells you that the parcel is on its way and it's time for you to pay me the money. Day 2 the buyer never pay a cent and keep hiding his face from me. So I will call up pos office and stop the parcel from being delivered.

Is this possible and is this a good way to conduct a deal which involves large amount of money and a far distanced buyer/seller?