Is there a way for foreigners to store their belongings in Korea for a month?

I need to safely store my luggage for a month before leaving Korea, but I'm struggling because I don't have a Korean phone number. I've looked into T-lockers at the airport or subway, but they are designed for short-term storage, making long-term use difficult. All the self-storage companies I've checked require a Korean phone number for membership registration. Is there a way for a foreigner to store large luggage for a month without a Korean phone number? I'm particularly curious if there are places in Seoul, especially near Gangnam or Hongdae, that offer such services, or if there are other alternatives. I would appreciate any help from those who know how to solve this issue.