Laugage complaint

I cannot believe the inconvenience I've been subjected to by SA Airlink. After boarding their flight from Johannesburg, I land in Mthatha to be told that my luggage was left behind in OR Tambo because it was too heavy and it can only arrive tomorrow morning. First of all, they weighed my luggage at check-in and no complaints were raised there, secondly they did not even bother to let me know of this decision prior to my departure. I am beyond annoyed at such disrespect - what gives SA Airlink the right to control my life like that? Do they know what my travelling plans were after I landed in Mthatha, if I incur any costs as a result of this inconvenience will they be liable? My suitcase is only tied with a cable tie which they can easily break, open my suitcase, take whatever they want and then close it with another one??I will not even be able to sleep tonight- praying I get my luggage intact tomorrow morning.