Dissatisfied customer service

Waiting for refund after I cancel health saver in December 2018. Momentum said they paid into my account in June nothing reflecting and they refuse to provide proof of payment. Have been waiting from beginning of July for this issue to be resolve . Have forward documents they wanted No one senior bothers to phone back. Is it so hard for them to pay your money back!!. Endless calls made to them only allows me.to speak to service consult