Student overdraft denied

Hi, can anyone offer help
I've applied for Lloyd's and natwest student accounts which I've been accepted and I've applied for overdraft for both and been denied. I've rung natwest they've told me they can't see a reason why I have been denied but they can't help as its all online. My credit score isn't great but its not terrible so I'm not sure why I'm being denied as I've heard student overdrafts are more lenient in relation to credit score etc.. What else can I do?