I would start with the homepage where you list services. You tried to list them in "columns" but the second and third ones are lower. My guess is your using wordpress?
Secondly I would create pages for each services so you can explain them better The reason for creating pages for everything is more chances someone will find you when they do a google search.
I think selling t-shirts on your site is a bad idea, as ef200098 said give them away. Their your customers. But if you do sell them, do it at request, putting that on the website just doesn't sit right in my mind and if I was looking at your site from a consumers perspective it would put me off a little. Your website should be more about your services and not "Pay your bill" "Buy t-shirts" ect.