To access O2 voicemail, you can dial 901 from your O2 mobile phone. If you are calling from a landline, you can dial your mobile number, interrupt the greeting by pressing the * key, enter your four-digit PIN code, and follow the prompts to listen to your messages. If you are abroad, you can call +44 7802 090 100 to retrieve your voicemail messages. If you need to turn on voicemail, you can dial 1750 free from your mobile phone. If you need to change your voicemail PIN, you can call 901, press *, choose option 4, and follow the instructions.