Nokia 6233 is a phone which belongs to S40 Series and thus doesn't have the possibility to install a Symbian .SIS file containing a Call Blocker application. For this feature to work properly, the phone needs to run the blocking application in the background and since it's not possible due to the limitations of the phone you will not be able to make it work, instead you should contact the network operator because they have the ability to block numbers based on a request. Upgrading the phone to a S60 series will solve this problem because S60 series phones have native Symbian with all the features required in order to run SIS applications in the background for active monitoring.
