Hi all, I'm trying to setup whatsapp for my kids so we can stay in touch, but need a mobile number to activate it. They don't need a sim card at this stage of life (always in range of wifi), but wondering what you ozbargainers think is the cheapest way to get a sim card and number just for verification without loading up with credit? Maybe one of those $2 starter pack sims with $10 credit included or something like that? Otherwise what's the cheapest starter prepaid provider? I only need to receive the verification text, it won't be used beyond that. I'll need to get 2 of them. I've tried the various free US VoIP number methods with no success. 
Thanks in advance!
Free or Cheap Mobile Number for WhatsApp

Comments
 - Thanks for the quick reply! So the Telstra $2 sim can be registered without credit and will be able to receive the whatsapp verification code without credit I guess?  - So the Telstra $2 sim can be registered without credit and will be able to receive the whatsapp verification code without credit I guess? - The $2 sim that is actually free and you are 100% correct. 
 As long as they are in Wi-Fi range (since the sim has no credit) you contact them via WhatsApp
 
 
 - My kids has ipads for school. Their ipads do not have simcards so we couldn't use whatsapp, we use skype for messaging. 
 - Aldi would be best as I think it has long expiry.  - 365 days 
 
 - Just keep in mind, if u ever had to switch devices, whatsapp could ask u to reverify your number. So if the number has lapsed for not recharging, u would lose the account and need to re register a new whatsapp account again 
 - Thanks guys this thread helped. Popped a $2 Telstra sim into a phone and didn't even have to activate it. Whatsapp downloaded and verified without problems. 
 - FYI, I just wanted to set up a cheap whatsapp account, and one way of doing it is to purchase a landline number (39c/month from Crazytel, temporarily forwarded to my mobile) and use WhatsApp Business instead of WhatsApp, as this will allow you to verify Australian landlines. - This has the advantage that you'll retain control of the number for a minimal amount of money and no further interaction (i.e. recharges/sim ports). 

aldi $5 sim with $5 credit for emergency calls on telstra network
or
$2 telstra sim but not credit included (same as optus/voda)