[Q] How do you clear notifications?

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I don't know how to clear notifications for my SGS2 and is there like a trick to forcibly wipe all notifications and make them stay wiped?

Cos basically:

1) t-mobile uk voicemail is chargeable, so i switched to hullomail
2) t-mobile uk then sent me a voicemail to apparently reset up the voicemail with them. **** that, waste of my 10p to dial the notification.
3) I want something to wipe notifications next time t-mobile pulls this dirty little trick.