which country are you in? What is your tariff called? You may not have received an invoice yet, do you mean an info SMS?

I am in Ghana, and i have a contract where i pay 49.99 monthly, in this bill there was another section in the bill titled “"Verbindungen & services”” where i was charged 189.21

i do not understand 

In Ghana, connections [calls, mobile data] cost extra. So the question again, what is the name of your tariff?

I do not know the name of the tarriff, it just says roam welt zone 4 or something 

Do you know how i can contact the billing department 

by phone, from Ghana call +4989 78 79 79 456.

What about by email or whatsapp chat

no, not the billing department.

Please check the invoice for the service types. The data costs in zone 4 are actually limited to just under €60. Therefore, there must be a reason for the additional costs. This could also be telephone calls.
It also takes some time to create the invoice. If you were only abroad 2 days ago, then the bill is probably from the previous month.

Hello @Afra Aba,

welcome to our o2 Community

Thank you for contacting us with your request. I've been happy to take a look at your contract.

Our security department have already informed you on May 31st via text message that these high charges for international calls from abroad have been incurred on your phone number.

You can find the charges for calls in World Zone 4 in our price list on page 5. Please note that incoming calls are also charged.

The charges have now been billed with your current invoice. If you would like to make a payment arrangement, you can contact us by phone on 089 787 979 456. Unfortunately, this is not possible here in the community.

Best regards

Giulia