What must a person do if they are indebted for a phone bill in another country, and the currency of their home country has changed, making the payment now exorbitant, knowing that they tried to pay it before their travel but were unable to?

The value of the invoice is a debt that must be paid. The Permanent Committee has issued a fatwa stating the obligation to promptly pay debts and clear one's liability from them. A debt is repaid with its equivalent, not its value, and it is not permissible to link it to price levels, inflation, or the price of gold and silver. Therefore, the questioner must pay the invoice value in its original currency, unless it has been reduced through an agreement with the creditor. Delaying payment is harmful to the creditor.