Testing function contains an API request

I'm trying to test my rails application which using Stripe APIs, So I started with models, I'm using Rspec, The model which i want to test is called bank_account.rb inside it there is a function called (create_bank_account) with argument (bank_token) its pseudocode is something like this:

def create_bank_account(bank_token)
  # make a Stripe request and save it in local variable
  # save needed data in my bank_account table in my DB
end

when i started to test this function, I found that there is an API call inside it, Which is not good, I need my test not to depend on Internet, So after searching I found 'StripeMock` gem, It is useful and i started to use it with Rspec, but I found my self writing a test like this:

it 'with valid bank_token` do
  # create a double for bank_account
  # using StripeMock to get a faked response for creating
  # new bank_account
  # expect the doube to receive create_bank_account
  # function and response with saving the data inside the DB
end

but after writing this I noticed that I didn't actually run create_bank_account function i faked it, So my questions are:

1- How can i test function that includes API request but run the function it self not faking it?

2- I read a lot about when we use doubles and stubs and what i understood is when a function is not completed, but if the functions is already implemented should i use doubles to avoid something like functions that call APIs?