Can anyone identify this every green please?

I'd be very grateful if anyone is able to identify this plant for me. I'm baffled, and so are the experts at my local garden centre. It's evergreen, with woody stems, and bears white flowers in July (not quite open in these photos, which were taken yesterday. It's taking over a bed, and I need to know how to prune it. Many thanks, if you are able to help! Sent from my iPad