Twice billed and used existing equipment

I paid ADT R3016.44 for a new alarm system on 22 April. 8 days later a debit order went off for the same amount. I thought my acount will be credited with the extra amount, but they debited my acount again for the monthly amount.The system was installed, but they used the existing keypad so I then paid for a keypad that I did not get. I was not there to oversee the instalation, but the feedback I got did not explain anything (no manual or instructions on how to use the system). At this moment I am thinking of changing to a different company as I am highly disappointed.