It is the service provider, i.e., the company that provides the service to you, who decides if a refund should be made. A refund can either be made on a future phone bill or by depositing the money into your bank account. It is common for you to choose the method you prefer.
If the refund is made on a future phone bill, the operator will credit the amount on your phone bill. Note that it may take several months before the amount is credited to your account, depending on the operator's billing process. You will need to pay the incorrect bill if you do not make a special agreement with your operator to only pay a part of it. The advantage of this procedure is that you do not have to share your bank details with the company.
If the refund is made by depositing the money into your bank account, you will have to share your bank details with the company. If you do not feel comfortable doing this, you can create a new bank account specifically for this purpose. If this account does not contain any other money, you should be able to safely share this account number. You can also consult your bank about this. The advantage of this approach is that you should receive the money within a few banking days, and then you can use the funds to pay the entire original bill to your operator.
We want to emphasize that it is outside the scope of Telekområdgivarna to handle questions regarding refunds and therefore we have not set any rules for how it should be done. However, we can inform you that many companies that provide premium rate services use the method of refunding directly to the complainant's bank account. We have handled many cases where complainants have received refunds in this way, and we have not received any complaints afterward that any problems have arisen in this regard.