Scroll Bar not working on phones

Hi I am having problems with a website some else has coded, it has been live for years but now I have had a phone call from the owner of the restaurant saying that people are looking at the food menus on their phones and the scroll bar isn't working on certain ones. It works on my iphone but it is invisible and most people probably won't know it is there. The problem page is:
http://www.cowshed.uk.com/menu.php

The css code creating the scroll is:

{CODE}
div.scrollable {
margin-top:17px;
margin-left:20px;
width: 300px;
height: 240px;
font-size:11px;
color:#FFFFFF;
font-family:georgia;
text-align:justify;
font-style: italic;
overflow: auto;
line-height: 14px;
}



It seems to work fine in web browsers

Does anyone know how I can get round this?

Thanks

Faye