<human>: I am in Alberta, Canada.

So I am having a garage built and due to the slope in my backyard I needed a concrete foundation poured.  Now I have an ESTIMATE from the contractor for roughly $15,000 for the work which included the foundation and pad.  So I have not signed anything but he has completed the foundation walls and is now saying he miscalculated the wall heights and has given me an invoice for $14,000 and the pad is not done and would be an additional $5500.  So my question is where do I go from here.  I have been told to get a small claims lawyer or only pay him the price minus the 5500$ it would cost to have it done.

Can you provide a brief overview of the text?
<bot>: Received an estimate then the contractor did the work and then I received an invoice for the project that was the full amount without the concrete pad done.  39% increase to the original cost.