Have you read your actual policy document rather than relying on office banter in a call centre? With my Axa policy, the terms states I get 93 days cover in the EU in the duration of the policy year. It states that I can apply for an extension but this is not guaranteed and is subject to an extra premium.
So, call your broker or underwriter to request an extension and if that does not work, bin the current policy and buy a new one as I stated above.
Yes, most policies from the UK will specify the length of trip, and max days per year. It isn’t their intention to provide (say) an annual policy, which you can use for an unlimited number of days in continental EU.
Do it the right way, otherwise - how can you expect the underwriters to honour their side of the contract.