Have you reviewed your PDF invoice in Self-serve? It contains all the fine details of your bill. Your first billing period is pro-rated from when you signed up to the billing date. You are also charged services for the upcoming month in advance This occurs when anyone signs up with a provider. Similarly, when you change a plan, both the old plan and the new are pro-rated for the portion of the month they were active. Here’s link for you describing the process. http://help.koodomobile.com/my-bill/charges-explained
Then go to "charges on my first bill"
You're being billed for 34 days of service. You're being billed from May 17 to June 16, plus May 13 to May 16. How cool is that!
The good news is, generally speaking, all post-paid accounts regardless of carrier do pro-rated billing.
That means if you go onto a cheaper plan during your billing cycle, your following bill will have a small pro-rated credit rolling in. Same goes for going to a more expensive plan, you'll be back-billed the difference as a charge on the following bill.
Hoe this helps! On a different topic, I'll be in your beautiful town to celebrate Canada's 150th. Which restaurant would you strongly recommend as one not to be missed?