There are different ways to handle unwanted calls and block a phone number. All methods won’t work for all, so you would need to carefully choose an option which will work for you. Now a days, the handset manufacturers have started providing features to help you block phone numbers.
Here are some ways for each type of handsets available in the market :
Block Calls in Nokia Symbian
The Nokia symbian phone users can download apps which can block specific phone numbers from making a call. Here are some software of the softwares that can block calls for you
Black List Pro

BlackList application automatically rejects any unwelcomed call. The program is fully customizable and easy to use. There are custom rules that can contain persons from contacts, groups of persons from contacts, custom phone numbers, there are selective situations, tight interaction with Contacts, handy log and much more!
Download Black List Pro
Handy Blacklist
Handy Blacklist for Nokia protects your time and peace of mind by keeping undesired calls off your phone. It contains 2 types of lists, first is Blacklist which contains numbers you want to be blocked and other is Allowlist which contains numbers that will be allowed to receive while others will be rejected.
Download Handy Blacklist

Handy Blacklist for Nokia protects your time and peace of mind by keeping undesired calls off your phone. It contains 2 types of lists, first is Blacklist which contains numbers you want to be blocked and other is Allowlist which contains numbers that will be allowed to receive while others will be rejected.
Download Handy Blacklist
Block Calls in Samsung
By making changes in the “call restrictions” section of your Samsung phone, you can block people from calling you. Once the call restriction is set, you will not hear any calls come through your phone until you change the settings back to normal. All callers will be sent directly to voice mail. You can also set your phone so that certain callers will be sent to voice mail without your knowledge.
Blocking All Incoming Calls
1. Go to the main menu on your Samsung cell phone. Press “Tools & Settings” or the similar section listed under the first level menu options.
2. Press “Call Settings” or similar. You will be taken to a list of options for receiving your calls. Select the “Call Restrictions” option.
3. Under “Incoming” select “Yes” to program your phone to automatically reject all incoming calls. On some models you can also set the phone to restrict calls from anyone outside of your contact list, or only from callers who are on your contact list under the “Call Restrictions” menu.
Blocking an Individual Person
1. Save the person’s phone number in your Samsung phone’s address book. If it’s a bill collector or another person who you don’t know, you can save the name as something generic, like “Ignore” or “Block.”
2. Go to the entry that you just saved in your contact list and click “Edit.” Scroll down until you see “Sounds,” “Tones” or similar and press “OK.”
3. Scroll down again until you see “No Ring.” Select this option and then press “OK” to save this new change to the contact. From now on, all incoming calls from this person will be silent and sent on to voice mail without you ever having to hear the phone ring.
Block Calls in Sony Ericsson
1. Flip open your cell phone and go to the phone’s menu.
2. Select “Settings” and scroll down to “Calls.”
3. Select “Manage Calls” and then choose “Accept Calls.”
4. Choose to accept “All Calls,” “Calls from a list” or “None.” If you choose to accept calls from a list, you will have to create your list of accepted callers. This is easy. You will just scroll through your contacts and select numbers you want to accept.
Block Calls in Blackberry

If you have a Blackberry, you can use a program called Efficient Call Blocker from BerryWAV. This program will block numbers that you specify and let you make the other party hear messages like your number is disconnected or no longer in service. Although it is a premium service which costs 5.49$. You can buy it from here.
Other Application which you can use is CallsBlocker. It is a free software from Fabian. The interface is very easy to handle and manageable even for new Owners.You can download it from here.
Block Calls in iPhone

There is an app called “iBlackList” which costs $1.99 which can free you from thousands of telemarketers. iBlackList is an application that allows you to filter your incoming calls and text messages. After installing the application you will want to restart your iPhone. iBlackList is available through the iClarified source.
In case you have a jailbroken iPhone, there are couple of neat apps which will help you – MCleaner &iBlacklist.
In case none of the above tricks work then “Do not call” Registry.
This option is best suited if you are trying to block a telemarketer.
If you are in India, there is a National Do not call registry where you can register your phone number.
If you are in US, you can register with the National Do not call registry or call 1-888-382-1222 from the number you wish to block to keep the telemarketers at bay
source : weeklysmashing.blogspot.com