Drop into the bank ans pick up a copy of the Terms And Conditions for your account. It should mention all the Rules.
If you can't find the rule you were told about ask them to point it out to you.
This one sounds like one of those rules that isn't really a rule. I regularly get told that I can't do a particular thing, and next time with a different teller it turns out I can do it.
My favourite line is "Oh, I was allowed to do this last month, Are you sure?". Quite often they are not sure at all.
I've been told by many people that if they lodge a cheque from a different bank to their account, it takes a few days before they can access it through an ATM. I've never had that problem. I think Bank "Rules" are a lot more fluid that we sometimes think.
-Rd