TOPIC:

I have replaced the battery in the key fob three times in a month and not with cheap ones and the correct battery number

However once the engine is started it says the 'battery needs replacing' on the message panel

Any suggestions as to whats wrong or do I needs to reset something

Afternoon 
first of all good call by using quality batteries I have read elsewhere that the key fobs don’t like cheap ones
with regards to the warning not going off I seem to remember when I changed my battery in the fob  I read somewhere that to reset everything you have to stand outside the car and lock / unlock it 3 or 4 times 
hope this works/ helps 

I made note to myself and it says
Battery LOW
Low message after replacing battery.
Press one of the buttons on the card four times close to the vehicle. The next time the vehicle is started, the message will disappear.