I don't think you fully understand what a spending cap is.
A spending cap is a limiation placed on postpaid (monthly) accounts. When you sign up on a monthly plan a credit check is done. If you don't have good enough credit, Telus will put you on a spending cap to make sure your balance never goes over a certain amount. In the case of a spending cap, it's $200. This is not something you can just choose either. If your credit is so terrible that you are rejected, you can't choose a spending cap. The system chooses what you are allowed to sign up for based on your credit.
When a Credit is accessed on an individual a spending limit may be placed on an account. This is based on whether the customer has no established credit or poor credit history. If this is the case you would be placed on a spending limit which will cause an interruption of service if at anytime your account exceeds $200 if this happens Telus would require a payment to bring the account balance down to a certain amount which would consist of any billed charges plus any unbilled usage to bring the account down to $100 or whichever is greater. This Spending Cap will remain on the account until acceptable payment history has been established with Telus-Usually 9-12 months of excellent payment history after that point the spending cap is removed from the account