Another optus prepaid customer who received a call from this number.. i didn't answer it and it just rung out.. rang for about 15 seconds

I got  a missed call message just after 5pm it seemed strange as i did not recognise the number i had thought of doing call number block to see who it was but i dont think so after reading this

i got called by this number today and missed it.i  am a optus pre paid customer  and i have had optus ring me in the past and offer me new deals and they have been optus deals.i never answered the  call but i will next time to c who it is.

I just got the call...told me they were from Optus offering em a new plan. I have prepaid. How did they get my name? I was suspicious as Optus usually send an sms with new plan options or tell you about it when you recharge..... Wonder what company it is?

I received this call yesterday but they left no message.

im getting it constantly now and am absolutely fustrated! how do i stop it!