Best answer by Mathieu
In self serve you have access to your last 17 bills.
As for your tab, technically it should always be going up (unless you have a new plan, but I'm going to assume you are using an older plan with at 10%/15% Koodo contribution). If for example you started at -150$, you want it to go up to 0$. Once it reaches 0$ it will keep climbing up to 150$ this is a tab credit you can use towards the purchase of your next phone.