You should open a new Billing Support Request. Below is link to open new billing support request in portal:
It will look similar to below sample screenshot:
Enter summary, select Problem type, select Problem subtype, then click Next. After a delay, some potential solutions will be shown. Click Return to support request as shown below:
This will return you to the recommended solution tab. Click Next, as shown below:
Fill out the information on the Additional details tab making sure your email address/phone are correct, click Next, then finally click Create. At this point your support request will be created and you should receive a Case email from Microsoft Support and will be contacted in near future by support engineer.
If the above was helpful, please click Accept Answer.
Create a new support request and discuss it with the person that is assigned to your case. You can select the option for them to call you. You don't have to select refund request, you could select Unexpected charges instead.
Last billing case I opened at beginning of business day and they responded within about 2 hours.