How can I send a text message asking for money if I owe money?

Just call directly and say that money is a little tight now. Give me back the money you borrowed from me last time. That's your money after all. Do I need to ask someone else to return it? Of course, if you don't pay back the money you owe, you have to look after it yourself. Now there is a saying that if you want to lose a friend, lend him money.