You need to submit a billing support request by following https://learn.microsoft.com/en-us/azure/azure-portal/supportability/how-to-create-azure-support-request
You can try https://support.microsoft.com/en-us/topic/customer-service-phone-numbers-c0389ade-5640-e588-8b0e-28de8afeb3f2 but the proper way to communicate regarding billing is by using the first method
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hth
Marcin