Caller: I don't know

This text message arrived in the early hours of this morning from: 0484 641 991. I'm not an account holder of the company they're purporting to represent, i.e: East Link. They're asking for action urgently to avoid penalties on my toll bill payment. They've been blocked on my phone, but they continually to change, in only the slightest way, the East Link part of the message.