Etihad...or South African Airways?

I recently traveled to London, UK via Abu Dhabi with Etihad Airways. Although, I thought it was Etihad Airways. It was only when I was presented with a boarding pass for the Johannesburg to Abu Dhabi leg, did I realise that I would be travelling South African Airways. I had the same experience on my return to South Africa, the leg from Abu Dhabi to Johannesburg was also with SAA. It was only the route between London and Abu Dhabi which was Etihad Airways. I am not sure if this is the norm, but if the level of service between the two air travel providers were the same, I would have no complaints...but Etihad are of a far higher quality in every way. Surely, if I pay for an Etihad Airways flight I should expect to get Etihad from the start of my journey. Any assistance or clarity on this matter would be appreciated. I have emailed Etihad via their website, but have yet to receive any reply.