Customer charge at the CenterPoint energy bill

I've just received the bill with the following line:

• Customer charge ~$20

As per their definition:

Customer charge and base amount. Covers fixed costs for reading meters, issuing bills, maintaining facilities and gas lines, postage, etc. These costs occur even if you do not use gas during a billing period.

Does any of you know how they get this value?

Why it is $20 and not $200 or $2000?

Have we signed up to pay such 'charges'?

p.s. I haven't been able to get any reasonable information from their customer service.

We've explained what the charge is for and how it's governed and approved by The Texas Railroad Commission. We've answered your question to the best of our ability.

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