How do I access PhoneUtil settings?

[AC Question]

I need to access the PhoneUtil app, however, when I enter *#7284# into my dial pad and press call, it says "USSD code running...", followed by "Unable to process request". I'm using a T-Mobile Samsung Galaxy S5, unlocked and rooted, currently on Wind Mobile in Canada.

I very desperately need to access PhoneUtil, any help would be appreciated.