Remove Commerce Payment Method Pane?
You'll need a custom module with the following function:

function yourmodule_form_commerce_checkout_form_checkout_alter(&amp;$form, &amp;$form_state, $form_id) {
 // Do something here
}


You'll probably want to add a dpm($form); (assuming you have Devel installed) to get the exact item, but the array you'll probably want to target is:
$form['commerce_payment']['payment_method'] by perhaps setting the #access to FALSE if you only have one choice. In other words, add the following:
$form['commerce_payment']['payment_method']['#access'] = FALSE;

Be sure to clear the cache after adding this function.