Leaving o2 feeling robbed and extremely disappointed

[Mikes1982]

What's the best way to leave o2 I have been trying to for 2 days but the online conversation says disconnected I have been robbed for 18 months with very little or no satisfaction from o2 being charged about £15-£20 extra/month other than other networks it's an absolute joke then o2 want me to give them more money to stop myself being robbed absolute joke I will never use o2 ever again after being a loyal customer for 20 odd years god knows the thousands of pounds I have been robbed

[Cleoriff]

@Mikes1982 

How to cancel your contract here Guide: Cancelling Your Contract 

Just wondering if, as you say, you have been overcharged for 18months, you haven't done anything about it before now? If you wish to make a complaint then follow this guide https://www.o2.co.uk/how-to-complain 

[jonsie]

Can you clarify exactly how you have been robbed @Mikes1982 ?