Question on additional charges

We have been using Zendesk with Voice for nearly 2 years, and recently, I noticed a weird charge on our Voice channel. So we have opted for 3 phone numbers, and 2 of them are at USD5 each and 1 of them are at USD7. So total comes to USD17, which is okay. These 3 numbers can also be viewed in Admin Center>Channels>Talk>Lines.

However, we are also being charged for 2 other numbers, one at USD5, and another at USD75 a month. Both these numbers are not found listed under Lines and we are have not seen this number as well.

When I reached out to Zendesk support, I get this answer below, which is very vague, and does not answer the question:

"Upon double-checking the number (XXXXXXX) it is a Singapore number that you have purchased. Now the XXXXXXX is a Malaysian number on your account. You are maybe using those number for international calling hence the bill."

Can anyone advise me more on this please?