A call blocking program is available for Nokia phones using a newer version of the Symbian operating system. Based on my research I have come to conclusion that your phone was discontinued and also it does not have an operating system which features software installation. There is no way you can use a blocking application and I see the phone supports Java MIDP technology but it is not enough because although you find a call blocking application for Java you will have to keep it open in the foreground window which is not very handy. My only recommendation is to upgrade your phone to one which features the latest Symbian operating system then the solution is easy because on the market of the Nokia phones there are plenty of call blocking applications.
Another solution is to contact your carrier support service and explain the problem (regarding call blocking) and then based on an agreement they will block the offensive calls you specify.