The Optus Staff that are active in the Yes Crowd do not have access to Account Details, Billing etc. Have you logged into your account and checked your usage? Exceeded your data limit.
Is there any outstanding bills?
If you setup a Direct Debit of Optus after a bill was issued the bill needs to be payed manually then the direct debit kicks in for subsequent bills.
I got caught with this when I joined Optus, I checked my online transactions the morning after my first Optus Bill was due and saw no money had been taken despite my direct debit setup and it cost me about $1 for being late.
This is the only time I have ever come across a direct debit policy like this and what confused me was when I setup the direct debit Optus did the usual test transaction of a small amount which showed up in my account transactions, so I thought everything would be okay.