What is the mailing address for purchasing power?

Could you please clarify for me, where exactly can I find the mailing address for purchasing power? I'm interested in initiating a transaction but I'm having trouble locating the correct postal address. Is there a specific department or section within the company that I should be addressing my correspondence to? Alternatively, is there an online portal or customer service line where I can obtain this information more efficiently? Your assistance in this matter would be greatly appreciated.