Extremely disappointing response from Google

Its been a month now and Google still can’t explain why we were charged double for several months

Why are we charged double the hours for e2-custom-4-8704 (4 vCPUs, 8.5 GB Memory)?

Hours used vCPU Hours / vCPU
Compute Engine e2-custom-4-8704 (4 vCPUs, 8.5 GB Memory) 5,885.1 4.0 1,471.3
Compute Engine e2-custom-4-6144 (4 vCPUs, 6 GB Memory) 2,968.3 4.0 742.1
Compute Engine e2-highmem-4 (4 vCPUs, 32 GB Memory) 2,968.3 4.0 742.1