Murabahah is the sale of a commodity for the price at which the seller has purchased it, with the addition of a stated profit known to the buyer. The only features distinguish it from other kind of sale is that the seller expressly tells the purchaser how much cost he has incurred and how much profit he is going to charge in addition to the cost. If a person sells a commodity without reference to the cost, this is not murabahah.
If the facility is restructured, say extension of repayment period, the bank cannot charge additional profit for the extended period.
NB: A reminder that funds for financing under Murabahah contract should not be accessed by the customers but remitted directly to the vendors/beneficiaries as per proforma invoice provided at application stage.