Is it religiously obligatory to pay an additional sum to the housing company after it became apparent that the apartment's area is larger than what was agreed upon in the contract and the attached blueprint?

If a land or house is sold with a specific area, and it turns out to be larger, the sale is valid. For the one who was unaware of the increase and whose purpose was missed, there is a choice between upholding the sale or revoking it. The seller has the option between upholding the sale or revoking it. The buyer also has the option if he does not possess the price of the increase or does not need it. So, each of you has the right to revoke the sale, unless the seller voluntarily gives up the increase. If he insists on the price for the increase, then either you both revoke the sale, or you reconcile on estimating the price of the increase. And if they agree to the decrease or increase, it is permissible.