Picture Ratio- 1 Channel only

About a month ago, the picture ratio on DStv Animal Planet went completely out of focus, but all other channels were fine. Contacted Multichoice and they said I must take decoder in for testing which I did. Service was not bad, and received a new decoder, which is HD although we do not have HD televisions. After costly changes from our side to get new HD decoder working, Animal Planet was still not right although all other channels work on the Letterbox setting. I e-mailed the enquiries at Multichoice and they reacted quickly trying to give me instructions how to set the picture ratio, tried but nothing works, I don't think they really understand the problem, why are all other channels working accept Animal Planet, which was fine 1 month ago, and how can I set the picture ratio if it works on ALL other channels? How do I get this problem solved, Animal Planet is one of very few family channels and does that mean we have to buy new HD television which we cannot afford. I am just of the opinion that we pay Multichoice for the whole package and they should be responsible to see that all channels work. For the record, it's all repeat programs that use to be fine so what changed now?