So I went to the bank of china yesterday to ask them to change my union pay bank card to a credit card since my salary is wired transferred to my Chinese account and their answer was first you can't because you are a foreigner. Is that true? I don't master the mandarin language but that's what I understood.

Plus I also heard that I could actually get one if I buy a property, is that also possible?

Yes and yes.

I don't know about Bank of China but China Merchants Bank which is voted the best retailor bank in China for 5 consecutive years does have credit card business for expats. You can apply for a credit card by presenting copies of your photo ID (passport, work permit, residence card etc.), certificate of owing long-term assets in China such as real estate, bank deposit &/or salary income, and get a Chinese citizen as contact person (not a guarantor) in addition to yourself. Usually for first-timers the limit will range from RMB 25,000 to 50,000 and if you have a good track record for three years, it can be doubled.