Adding a call to debt. Purchase a receiver swaption. As rates move down, debt is still outstanding. With callable debt you would call the debt and refinance. Receiver swaption pays higher interest rate than the market rate as rates have decreased. As rates have decreased, you can either sell receiver swaption for PV to another party, settle for PV from swap dealer or enter into offsetting position (pay fixed, receive floating) at market swap rate pocketing difference.
i.e. Buy 5% receiver swaption. Market rates now 3%. I can’t call my debt and issue at 3% but I can enter a swap to pay 3% fixed receive floating and exercise my swaption receive 5% fixed pay floating. Net payments 5% income, 3% outgoing, receive floating, pay floating = 2% and pay 5% on debt. Net debt cost of 3%.
Subtracting a call from debt. Issuer paying higher than market rates based on having call provision in debt. Sell receiver swaption (fixed rate payer) as you think rates are going up. PV of swap offsets value of long call. Rates move down 5% to 3% in the example above. I call my debt, issue at 3% market rate and the swaption is used against me. Rate is still 5% however my effective rate is now the same as if my debt was not callable as I received the swaption payment.
Market rates 5%, I am paying 5.5% because my debt is callable. Sell receiver swaption. PV = .5% over life of loan. Now I am at market rate of 5%. Rates move down to 3%, I call in my debt, refinance at 3%. Receiver swaption exercised against me, I pay 5% receive libor. Enter offsetting swap at market rates, receive 3% pay libor. Net debt expense = 3% on newly issued debt, pay 5% on swap, receive 3% on second swap, pay libor, receive libor. Net effect Pay 5% which is the position I would have been in had I not had a call to begin with.