If you need to access your voicemail from another phone (landline or another mobile) make sure you have set up your voicemail PIN (Personal Identification Number) beforehand.
To access your messages dial your own mobile number and let the call go to voicemail. As soon as you hear the greeting press the * key. You will then be asked for your PIN number and will have full access to your voicemail box
You can also access your voicemail by dialling 07953222222 (+447953222222 if abroad) from any landline or non UK mobile, and follow the voice prompts. You will need to enter your mobile number and your PIN to retrieve your messages.