DSTV Now (People Logging in with old password)

I am using my mom's premium account to watch the channels on the laptop. This account has been shared with other people previous, so i decide to change the password and remove other devices so that they don't give me problem when i am streaming online. I have changed the password a month ago and to my surprise i still get the message that it has reached maximum device, i keep removing devices meaning that the people are still able to login with old password. How is it possible that i have changed the password and people can still login using the old password? Can you get this sorted out people, it's really frustrating. The customer number is: ***0 and the username to login on Dstv now is : *** Please sort this out , the password that i changed my sync and not allow people to login with old password.