You cannot get unlimited data on a Telstra prepaid plan, nor can you get the excess speed-capped data available on the provider's postpaid SIM-only plans. If you're looking for the options that offer the most data, your best bet is likely to be the $60 Telstra Prepaid Mobile plan as it includes 60GB per recharge for the first three months. After that point, it'll fall to 40GB. However, if you're sticking with it for the long-run, you do get a little more for your money than the more expensive $300 Telstra Prepaid Mobile plan.