Why build your own company software?
There are many business applications and company software tools that are designed to be adapted to suit most businesses and these can be fairly in-expensive to use, the problem with these pre-designed programs is that you will never find one that is a perfect match to what your specific company needs are therefore trying to adapt them can be quite frustrating and can mean that you have to make compromises with what the system can do.
Most companies that use phone lines will want an integrated system that records calls and links them to existing records held on the system, however if you want a more advanced system that will for example bring up the record when the phone first rings you may end up paying more for it.
Sometimes it can be more cost effective to have a specific application built for you that does exactly what you want, with a system that you have a good understanding of to be able to train other members of staff to run.
Once built if your business changes at all it will be fairly easy to add on other strands to the application to suit your business needs.