Vodafone has become the second UK mobile operator to turn on its 5G network, offering faster speeds and the opportunity for new services.
The network is going live in seven UK cities, including Cardiff, London, Manchester and Glasgow.
Making a success of the service could be crucial to the firm which has seen financial losses and customer complaints in recent years.
5G networks offer more capacity than 4G with speeds up to 100 times faster.
It could also help support new technologies such as artificial intelligence, the internet of things, robotics, connected cities and self-driving cars.
The three other cities to benefit are Birmingham, Bristol and Liverpool.