How do you protect your phone privacy?

Hi,
     my kids keep downloading those online game on my phone, they even use my credit card to pay for it.

I did not wanna scream at them and make them feel bad about it.

my friend told me to download those lock apps to prevent all this, but I have never used an app like this before.there are lots of choices.there is one called APPLOCK with tons of good comments. but I heard that some company paid for all these good comments just to make you download and it's actually not good at all. is there anyone used APPLOCK or anything like it before?can you recommend me something reliable?


Please help.

Thanks!

I didn't find the right solution from the Internet.

References:
www.cnet.com/forums/discussions/how-do-you-protect-your-phone-privacy/

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