Hello,
What is your web service connection type? Is it loading in onLoad then it will loads the web service while opening the form it will connect to your web service and try to open it.
If you have code to call the web service then it will based on your calling in your code. If you write the code in onLoad method then it will calls the web service while form opening. If you have calling that web service in any button event then it will executes when user clicking on that button.