Renault's Incompetence results to Bad service

I have taken my vehicle for a oxygen sensor replacement two weeks ago at Renault in Parden Eiland. We have not been updated about the progress of the work and have insisted on calling the dealership everyday to find out, but they do not pick up the phones and even when the reception does and you leave a message they never get back to you. I have taken it to myself to go physically to their premises to inquire in person of which I was told that the part was ordered and had been dispatched a couple of day in JHB, but what was surprising was that no information I could be given about the exact position of the part ordered. Now my problem is that we as a family have made travelling arrangements of which we are at the verge of losing monies as a result of this inconvenience. I have, since yesterday been calling Renault SA to log a formal complaint and seek relief regarding this matter, but I have not been able to get through to any of their agents, because the phone just rings and all of a sudden keeps quiet. We are performing a ritual back at home in the EC and all of us (Five of us) have to be there otherwise the ritual would have to be postponed and the preparations have began already. This is really not on.