BMW is ripping us

We had a problem with our car, BMW 320i, it has been showing a sign for low engine coolent, we took it to BMW Rustenburg, they did a pressure tester and found nothing, but the problem continued till we decided to take it back and they said there's a licking pipe. We paid for that pipe to be changed in March this year, within a month the problem continued, my husband decided to take it back so that they can check it again, they did another pressure test and found a problem which will cost us R12000, after that pressure test now the coolent is literally licking non stop,.

My problem is: If the car was fixed in March. Why are we still having the same problem? Why do we have to pay again for something that was fixed? It clear that BMW didn't to their work properly, yet they want us to pay again. I feel like we are being ripped off for something that we already payed for.

Please help us hello Peter.