I can't say definitely for the HTC One, but for most Android phones these days, there is no longer a speed dial feature like that any more. It's replaced by the ability to place a Direct Dial widget on your homescreen or in a folder--just one tap, and it automatically calls that contact. The Direct Dial widget allows you to specify which phone number of a particular contact to call--the other Contact widget usually prompts you each time, asking you which number to call.