The new speech codec is a simple software upgrade on a cell tower base station meaning those using certain newer phones on the network should automatically benefit from the better call quality.
AMR-WB, the codec is already used in a number of European countries and in itself, and works well on existing Nokia 3G handsets though many will have to buy new handsets to fully benefit.
However with mobile networks becoming increasingly saturated, many could question whether the networks' infrastructure can cope with the increased level of traffic. And with social media and mobile communication applications so popular among younger people and students, high-definition calls could re-encourage phone calls over text and instant messaging.
You can hear a short demonstration of the new high-definition call quality by BBC technology correspondent Rory Cellan-Jones who tested the new service earlier this morning.
Orange and T-Mobile merged last year to accumulate a total over 30 million customers across the United Kingdom, which was initially questioned by EU regulators. T-Mobile customers at present will not be able to use the new high-definition call quality, however this launch acts as a precedent which other networks can roll out in the near future.
Would you upgrade your phone to get HD voice calls? Could this re-ignite the phone conversation over texts and instant messaging? Have your say.