********** phone usage

My boss had his phone ****** on 24th June. We arranged for blacklisting first thing on 25th and did a SIM swap same day. Since then, he is being billed with constant calls to Pakistan (!!!) and loads and loads of SMSes and MMSes to premium numbers - none of which he's making. I've written to their offices several times and have made numerous telephonic enquiries - only to be told it's being investigated. Last month's phone bill was R46k and this month he's already on R36k!!! It's still continuing and nothing is being done. His usual usage (which he has not exceeded this month) is R1,200 per month. I am horrified and don't know where to turn.