The contract has one month left, and contract date lines up with bill date, but the bill for the last month has gone up. Looking at the actual bill the discount runs out 9 days before the end date of the contract. There aren't any extra charges - it's just the reduced discount.
IIRC at the contract start the discounts didn't apply correctly and needed help here to fix, then at the first CPI rise the discounts needed fixing again, and at the second CPI rise this year the discounts showed wrong online for many - so after all that maybe there is a good reason for the discount to expire early but it's not explained in the bill.
It's not a lot of money but it's one more thing at renewal time - already complicated as the online page shows 3 or 4 different deals (12, 18, 24 months, and SoGEA) that seem to change every few days, plus an email offer and another on the main account page too.
