Delay/not receiving visual voicemail o2 UK

Hi All

Hope you can help. I have spent hours on the phone to o2 trying to resolve my issue with visual voicemail.

I bought the phone (iPhone 5 32Gb) from Apple and a sim only deal from o2.

I realised about 2 months ago that I wasn't getting visual voicemails through, one of the reasons I went back to o2 in the first place.

I have tried all of o2's 'advice' and they say it's Apple's problem and that they should take responsibility, however I can't understand how when the rest of my data is fine, why visual voicemail wouldn't work. Is there any setting on the phone which I could look at as I am at a loss.

I have tried:

rebooting

resetting

restoring with iTunes

checking the data settings

resetting the data settings

resetting the network settings

a new sim card

deactivating and reactivating voicemail

leaving myself a message

a different phone - the messages appeared on the other one straight away and then on mine when I reinserted the SIM card.

data types - seems to be equally badly on WiFi, 3G, Edge etc... sometimes they come through sometimes not.

Could it really be a phone problem? The tell tale sign for me was that when I was on the phone to the o2 guru all my messages pinged through, but nothing since. co-incidence?

I do also experience more dropped calls that I used to with T-Mobile. Could these be linked?

Any comments gratefull received! I was particularly abrupt with o2 phone support today but they're not letting me out of my contract without a fee - unreasonable since I am not getting what I pay for. They 'see my point' but they say as my data is working ok then it must be a fault with the phone.

VERY frustrating!

Thanks

T

21.5"iMac/iPad2/iPhone5