What's the best iPhone 4 pay monthly tariff for £21 or under?

I'm looking for a pay monthly tariff on any network that will let me have an iPhone 4, I want a tariff with unlimited texts and some minutes, preferably some data but data isn't essential, but I don't want to go above £21 per month. Where can I find a tariff like this?

Added (1). In reply to 'Will'
I do not care for the latest gadgets, I think they're over priced and unnecessary as the iPhone 4 does exactly what I want, as does the iPhone 5, but from what I know, the difference is the screen is bigger on the 5 and it's more expensive.

&Thank you for your reply, I saw this but I'm unsure if vodaphone are a good network?

How about you just buy a iPhone 5s or 5c because you are way behind on staying with the latest gadets, lol

Vodafone do a tariff of £21 for the free phone, 300 minutes and unlimited texts, a bit of data too, or i bought my Iphone4 and i pay them £10.50 a month for the same deal, but without the phone.

Vodafone have suited me well for years, the only compliant is that there are no warnings before you are about to go over minutes, but you can get apps to sort that. But it really depends on where you are and what provider gives you better signal as well.

You do know that the THREE YEAR OLD iPHONE4 was discontinued by Apple 2 days ago when the IP5S & 5C were announced

On 12/09/2012 the iPhone5 was announced IP 3GS DROPPED,
like the year before IP4S IN, IP3G OUT… On 10/09/2013 no maths IP5S IN

Apple only support LAST 3 iPhones, discontinued means no longer sold by Apple, any future upgrades will in the main be for supported phones some new apps just WON'T WORK re IOS 7, will in the main be themes which the IP4 will get

The 5Mp camera IP4 may be the cheapest when compared to other iPhones but to invest any money in an OVERPRICED device is severe waste as in 2 years you will be using a 5 year old device that came out in 2010. Many have already upgraded from the IP4 in 2012…
http://www.itproportal.com/2012/09/06/8gb-iphone-4s-version-be-introduced-iphone-5-launch/
http://www.gsmarena.com/...ew-490.php

There are newer phones better phones and they cost a lot less*** giving you more than the 8Gb on the IP4, you should look at eg Sam Gal ACE II or the Lumia 620 for phone with a secondary camera microSD expansion Wi-Fi, GPS, DUAL CORE… AND BLUETOOTH MEDIA TRANSFER (Sharing) which no iPhone even the IP5 has (photos / music Can't be shared if one phone is an iPhone )
Here are the specs only if these phones are Gold Plated will it come in above the IP4 http://www.gsmarena.com/...hone2=5147

If you were in"Orchardland" the above puts you in the IP4S region
{***Apple's branding!}

The HIGH spec phones are expensive I accept that but
The IP5S became the most expensive phone on the planet!
The 16Gb 32Gb 64Gb all cost £30.00 more the IP5 a year ago

This is the 3rd Dual Core phone by Apple which has a 8Mp camera the IP5 and IP4S before.
That the IP5S costs MORE than the S4 is down to people who do NOT know how to use Google or do any research.

To be clear
Many are not in awe of iPhone due to them having superior phones to the Iphone, eg on 09/09/2013
the IP4 was the 3RD best iphone available, The above two phones are mid range at best, in the 3 years technology has moved on!

NOBODY IS WAITING FOR APPLE TO CATCH UP

Who in 2013 buys a 2010 phone BTW the first Iphone to have a camera flash?