The Custom Price Book (CPB) may fail to apply rates from different billing rules in specified regions and instead the rate is getting applied to all regions.
Exclude the region on the billing file to apply UsageType to all regions https://apidocs.cloudhealthtech.com/#price-book_introduction-to-price-book-api
When the region is not specified in first rule, the rate is applied to all regions and the preceding rules are ignored.
Example: First billing rule has <UsageType name=“TimedStorage-ByteHrs”/>. This will apply rate to all regions. The resolution involves including the region name "e.g USE1" into the prefix as such <UsageType name=“USE1-TimedStorage-ByteHrs”/>
You will have to apply the same correction to all UsageType names that do not specify a region.