This all seems strange, but here are some thoughts.
Using wifi has nothing to do Speakout. You are using your own internet provider. (You can remove the sim card and still use your phone to surf the web.)
The only ongoing charge from Speakout is $1.25/month for 911 service. Did you check the call log on your phone? Is data turned off? (although if you've never subscribed to the data plan, you should have no access to it.) Do as Dennis says and call customer service.