If you apply for the BSNL Junior Engineer examination, perfectly through the proper examination notifications from the BSNL then  there are no scams. But if you are getting any message on your mobile number from unknow numbers, this may not be true and you can become a part of a scam. So be sure that you are applying in proper channels & if you are appearing through the proper notifications by BSNL then you have nothing to worry about this.

I hope this helps. All the best!