Sentences I need for work, please help me

Could you please help me correct these sentences. These sentence, I have to use at work, and would like to know if they are correct and if I'm getting what I'm trying to say across.

- The higher the price (gets/is) the higher up the list of rates you have to look to find it.
- You might have a hard time retain the order in which to do the task. but you'll retain the procedure more and more as you go and the days go by.
- You are usually paid the following month for the extra hours you've worked.
- You never have invoices with/at the same amount of money. There are never 2 invoices at 147£.
- The number was off by 10 dolars. The paper said there was supposed to be 419 dollars in the till but there was 409.
- If the amount on the invoice matches/corresponds to the number in the log, then what are the chances that the name on the invoice doesn't match too.
- We get paid in cash.
- Even if there aren't as many transactions in American Express as in CB, the total amount in American express purchases is always bigger than the CB purchases as the amounts per transaction are a lot bigger when its an AX transaction.
- I need to bill the phone/do the billing for the phone for the day. (see how much people owe for the phone call today) (working at hotel)

Thank you