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“6. The address that you need to write to if you want to cancel your agreement with us has changed to: : O2 UK, PO Box 242, Houghton Regis, LU5 5WA
8. Ending the Agreement
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8.2 This Agreement may be ended either by you or us giving at least 30 days' notice. You must pay all Charges incurred during the Agreement.
8.3 If this Agreement is ended during the Minimum Period, you must pay the monthly subscription charges up to the end of the Minimum Period. This does not apply if you end the Agreement for the reasons in paragraph 8.4.
8.4 You may end this Agreement by giving us written notice if:
(a) we break this Agreement in any way and we do not correct the situation within 7 days of your request;
(b) we go into liquidation or a Receiver is appointed over our assets; or
(c) we increase Charges for your Inclusive Calls or your monthly line rental charge or change this Agreement to your significant disadvantage, provided you give us a minimum of 30 days written notice (and provided you notify us within one month of our telling you about the changes). This does not apply where the increase or change relates solely to Additional Services in which case you may cancel, or stop using, that Additional Service.
In the situations described in 8.4 above paragraph 8.3 will not apply”
Source:
O2 website
Click on [+] next to 'Pay Monthly Consumer Service Terms & Conditions (April 2006)'