Call to undefined method plgHikashoppaymentSisowIdeal::getCancelUrl()

-- url of the page with the problem -- : www.ijscomanvenlo.nl
-- Error-message(debug-mod must be tuned on) -- : Call to undefined method plgHikashoppaymentSisowIdeal::getCancelUrl()

I am using the Sisow ideal plugin in test mode. I get this error message.

I am using a valid merchantid and merchantkey.

What am I doing wrong?

Kind regards,
Hubert

Hello,

I'm sorry but we cannot provide support on plugin we did not developed.
Please contact directly the developer/support team of that plugin.

Regards,