You can upgrade at any time, but you would first have to pay back the balance of the subsidy that was provided to you at the time you purchased your phone.
If you check the website for the “No Term” cost of your phone, you subtract what you actually paid for the phone from it. You then divide the difference by the number of months in your term and you will get an idea of how much goes towards your subsidy per month. You can then subtract the number of months you’ve fulfilled from the total remaining balance and that will be your remaining device balance that you have to pay back in order to qualify for a new subsidy – usually on renewal.
If the device balance repayment is not an option on your account it may also be due to certain factors, like being on a spending cap. if you recall when you signed your original term with your current device if that was offered instead of a deposit that may be the reason. Best option is to go to your local Telus store and find out your options if you are not sure.
If the account is on a spending cap, or is inelgible to be upgraded at this time, a good payment history going forward will allow the cap to be removed or the payments to improve. After 9 months of good payment history you would be eligible to be upgraded.