Choose the column based on what you paid. It depends on which province you live in if it was GST or HST. Zero-rated and exempt usually are food and residential rent.
The column you claim your expenses under will not affect your Employment Expense claim, but if you are claiming the GST/HST rebate (GST370), it's important you enter under the correct column.
In your case you should enter the total of your phone bills + the tax you paid (GST or HST) under that specific heading.