Yes, bet365 is a trustworthy online gambling site. They are licensed and regulated by the UK Gambling Commission and have been in business since 2001.

To change your bet type you need to select your current bet type at the top of the bet slip, for example 'Treble'. Once selected a 'Change Bet Type' pop-up will appear allowing you to choose from all applicable alternatives. Each bet type will display alongside the number of bets included and the new unit stake amount.