Wasn't there some kind of scam people used to pull where they'd add a prefix to a cell phone's outgoing calls, such that it bounced through a paid service relay

Wasn't there some kind of scam people used to pull where they'd add a prefix to a cell phone's outgoing calls, such that it bounced through a paid service relay? If I recall, someone would nab your phone, add the dialing prefix to the settings, and then return the phone to you. From that point on, all outgoing calls would actually be calling a 900 number, which then just called the outgoing number. The phone's owner would then get caught with a massive bill from the 900 number. It was an updated version of one of those original 'boxes', maybe a modified brown box? I forget all the phreaking terminology now, but I wonder if there's another olde timey phone phreaker trick that could be exploited.