The Financial Times has an interesting article explaining how prices could rise if Three and O2 merge, but it also states there could be benefits in terms of network quality.
On the downside, it points out how Three has challenged the big players by packaging 4G superfast mobile in “all you can eat” data bundles. Three has also campaigned to cut roaming costs for consumers, and to lower the cost of connecting calls with the larger groups. This is likely to end with an O2 merger.
The paper points out that where mergers have happened tariffs rise. It cites Austria where the move to increase the cost of mobile tariffs was almost immediate It reports Ovum analysts as concluding "that “the biggest concern now will be what happens to consumers, particularly at the lower end of the market, which Three catered very well to”.
http://www.ft.com/cms/s/0/5b937fea-a...#axzz3PgrLLIVT