Hello, my first time posting here ...

Grateful for any advice or thought of the obvious things I may have missed. Apologies in advance as this a bit long winded.

I have received a daily service from a company for 9 mths, with a daily rate agreed, and billing every 30 days - ie the same amount paid every 30 days. I used this service for 9 mths, paying every Invoice on time and in good faith. I stopped using the service at the end of August, all Invoices paid.

I have received an email from the company requesting to pay an additional amount on an Invoice from January 2017. The email states 'there is a small unpaid portion' due too incorrect dates on the invoice and would I be kind enough to make up the balance.

They have sent me a summary of amounts Invoiced and payments received with a discrepancy in their balance of 3 days. They have also included all their Invoices however, many of them are not the ones I actually received and paid from, they do however cover the correct time period.

The invoice in question, was one I received and stated it was for 30 days x daily rate = expected amount, however in the Invoice description the dates stated were for 32 days and not 30. This is where they say I owe 3 days. I say it is for 2 days.

This discrepancy in date was followed through for all the remaining Invoices, so my logic says I have had a service for 2 days that I haven't paid for and need too rectify.

The confusing part of all of this ... they say I owe for 3 days, which I disagree with for the reasons stated above. (I believe I have evidence to prove why.) However, I have found a discrepancy which I believe explains their 3 day request. It is related to a different payment made due to a holiday break I had - i.e. no service required. I gave notice for the dates I would by away - 15/6 - 27/6/17 and it coincided that my previous 30 day period ended on the 14th June. I received a Deposit Request - note not an Invoice - for this 30 day period and paid, however I was still using their service on the day I left - the 15th June - and verbally spoke to the person sending the Invoices/Deposit Request about needing to pay for the extra day. The response was we know and its okay, Have it on us.
This member of staff no longer is employed there.

My question in all of this is do I highlight this to the company, as the Invoice they have sent me to show my holiday break in June is not the original Deposit Request I received and paid for. It spans a different time frame and includes the 15th June.
I assume its my word against there former employee's!

I have read that legally you can be invoiced for up too 6 years, so the time delay is acceptable to me.
I have also read of a phrase 'Errors and Omissions Accepted' used by companies too ease legal liability when errors occur. My Invoice (and all the others received) doesn't have this phrase on.

The amount in question is £1K+ which isn't a small amount of money to me at all!

Thank you in advance.