Despite O2 launching its 4G service at the end of this month, pre-pay customers will not know the price of 4G access "until the end of the year".

O2 is offering 4G SIM only deals from £26 a month and Pay Monthly contracts with a 4G device from £32 per month, when the service launches on 29 August in limited areas of the country.

O2 is also bundling music, sport and gaming content with its 4G deals. Vodafone has already said it is bundling Spotify music or Sky Sports with its 4G deals when it launches at the end of the month too, also in limited areas of the country.

The O2 4G bundles come with unlimited minutes and texts. O2's 4G SIM only packages start at £26 for 1GB of data and go up to £36 a month for 5GB of data. If customers need additional data, they will be contacted about "bolt-ons", which will be available at £6 for 500MB and £10 for 1GB.

Customers who also want to choose a new device have a range of options through O2 Refresh, which gives O2 customers the flexibility to get the latest device whenever they want.

Airtime plans for O2 Refresh start from £22 a month for 1GB of data, and go up to £37 for 8GB. Customers have the flexibility to choose a 4G device at a price per month that suits them. The monthly device payment will range from £10 to £25, dependent on how a customer choses to pay for one of over ten 4G-ready devices in O2's range.

But O2 said 4G Pay&Go and mobile broadband tariffs will "launch before the end of the year", with "more details coming soon".

Like most mobile operators O2 wants more customers on two-year contracts so that it can make more money per month. The popularity of expensive smartphones has turned more customers into contract holders, as they get the shiny new gadget up front and pay for it over a two year period.

It will be interesting therefore what phones O2 offers those sticking out for a pre-pay deal up to four months after the 4G service is launched. The advantage to pre-pay customers is that they are not tied down to a donkey of a phone for two years on a more expensive 4G contract, when fast moving mobile phone technology comes up with the next big thing.

Existing O2 customers with a 4G-ready device can transfer to a 4G tariff without needing to sign a new agreement, said O2.