I've done a 50% water change and the amonia is still high please help I've lost 4 fish so far don't want to loose any more

How many fish do you have in your tank and how large is it? The most common cause of ammonia poisoning is too many fish in the tank dirtying it and the filter just can't keep up resulting in the good bacteria dying. Another problem is dropping too many new fish in a tank at once or overfeeding.

You need to get the Ph levels around 7 or below (ammonia is more potent above Ph 7) and buy an ammonia treatment from the pet store.