Getting a refund for an invoice

Even if I cancelled my mobile subscription with KPN in July and I paid the invoice of it. This week I get another invoice from KPN for a service that I didn’t use. I think it is going to be taken from my account on 31 august. Is it possible to get a refund from this because I informed KPN service on phone that I won’t use it and I cancelled my subscription. I get another invoice from the company. My normal service was 35 euro and extra service cost comes as “0.69 €”. I would like to pay only extra cost. 
Looking for help