When outgoing call minutes and data are used up you will be charged pay per use rates
. In my opinion, those rates are expensive. They will be charged against your account balance, if there is one. If not I suspect the call will be blocked until money is added. In an emergency, it's possible to make collect calls but the rates for those is very high. Some prepaid sellers have automatic top up options that automatically add money when the account becomes low. That needs to be used with caution, or a very low limit credit card.
1-800 calls will count as air time and will be charged against voice time or at pay per use rates.
Note that retrieving voice messages is charged at $0.40/min. That's also quite expensive and should be charged against talk minutes, not always at pay per use rates.
Chatr is on the Roger network. My experience is that 3G data on Rogers network is not very reliable. If data speed and reliability is important, go with a reseller that has 4G.
This plan is fairly inexpensive as long as you stay within the allotted data and voice amounts. Otherwise, it could get quite expensive. If there is any chance pay per use voice or data is required, I would be looking elsewhere.