Singapore signed a mobile phone. Can I sign another one if I haven't paid back the money?

It shouldn't be possible, in which case you will be blacklisted. The visa should not come down.

But it will be difficult for you to enter the country again in the future, or you will be fined.

Let's pay back the rest of the money. Don't embarrass China people for a little money. Now SP/WP wants a deposit because there are too many people who don't pay back the money.

If the amount of arrears is quite large, and you are a non-Singaporean citizen, then the telecommunications company will probably ask the Singapore Immigration Bureau (not the Customs) to blacklist you, or, as you said, "you must make up the arrears before you can pass the customs. You have to ask a lawyer in Singapore and consult the relevant local laws.