CrazyCall is the most popular website used for call spoofing. Few countries have also blocked the website because of its use in many crimes. This website lets users make calls from any number they want. So, you can make prank calls with this. It also lets users change the voice to be anonymous while calling.
SpoofCard is also a nice service that lets users call from any number. You can call your friends from his number. It also lets you make group calls. For using the service, you need to have credits in your account. You can make demo calls for free, but you need to buy credits for more calls.
Spooftel is also a similar kind of caller id spoofing service. Purchase credits and make prank calls. You can also make demo calls to see how the service works. It also has option to change the pitch of your voice. It also has an option to send messages.
BluffMyCall is another nice call spoofing web service with lots of features. It lets users change caller id, record calls, change voice and leave voice messages. After using your free minutes, you can purchase your minutes.
CallerIDFaker comes with better offers. You can get unlimited calling for whole month only for $29.95. Like other services, it also lets users change voice and record calls.
Please use these websites only for playing pranks with friends. You can easily get caught if you use it for illegal work.