front end website and configuration payment gateway for voip switch . calling card

we have voipswitch which is windows based softswitch its designed for calling card, pc2phone, linksys adapter and callshop. By default it uses IIS, asapx for front end. We are interested to enhance and customize on line functionality making it easier for new customer to sign up , existiing customer to sign in, check their details , make payments. this functionality is already available , but we need some customization and cleaner look. most work is related to web development and addition of some tables in database and to pull relevant data from mysql . We can give access to a test server to check the details and add necessary functionalities. Final result should be a script which can be run and adds necessary functionality. Work can be done either in Apache , php . or IIS aspx