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A customer noticed that her bill amount increased on a specific month and I would like to ask her about it.

When did you start noticing extra charges on your bill?

In which month did you start noticing your bill increasing?

What month did you start noticing an increase of the amount of your bill?

When did you start noticing extra charges on your bill?

In which month did you start noticing your bill increasing?

What month did you start noticing an increase of the amount of your bill?

Are those previous questions correct? If no, what's the nature way to say them?

A customer noticed that her bill amount increased on a specific month and I would like to ask her about it.

When did you start noticing extra charges on your bill?

In which month did you start noticing your bill increasing?

What month did you start noticing an increase of the amount of your bill?

Are those previous questions correct? If no, what's the nature way to say them?

A customer noticed that her bill amount increased on a specific month and I would like to ask her about it.

When did you start noticing extra charges on your bill?

In which month did you start noticing your bill increasing?

What month did you start noticing an increase of the amount of your bill?

Are those previous questions correct? If no, what's the nature way to say them?

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Is this a question correct?

A customer noticed that her bill amount increased on a specific month and I would like to ask her about it.

When did you start noticing extra charges on your bill?

In which month did you start noticing your bill increasing?

What month did you start noticing an increase of the amount of your bill?

Are those previous questions correct? If no, what's the nature way to say them?