Fix a bug in our prestashop online shop

We are a growing e-commerce company, we got online shop selling printed t-shirts and other apparel. We are in search for a web-developer specialized in Prestashop CMS to help us maintain the running shop. For that project we need only small fix: At the checkout process, at the "enter your address" step, when you are a registered member who already have 2 or more addresses in his account, the button which you can usually use to "Add new address" doesn't appear, the only thing you can do is to choose between your already existing addresses. We want this button to appear when even when you have multiple addresses, but only when "Use the delivery address as the billing address" in unchecked. The work will be done not on the real site, but on some cloned-server (real git) which you will be given http browsing and SFTP access to. Thank you!