I also experienced the same problem. I also downloaded and installed the new firmware. I'd even restore it to its original factory settings and also switch network from Dual to 3G to GSM with different network provider and the problem still persist. I dont know what to do with this phone anymore.
Please nokia if your phone does not support any network in asia, then dont sell any.
If anybody knows how to fix this problem please post the solution here or post it somewhere where people can find it. So we dont waste our time and money buying such phone like this.
Welcome to Nokia Support Discussions!
Usually, call blocking is a feature you can get by downloading call blocker apps. Call Blocker apps are not available for S40 phones such as Asha 303. See this link for the explanation:
You can try to check with your network provider if they offer call blocking service.