Yan din prob ko kanina. Upon seeing your thread, ginamit ko rin yung *143# as suggested by the majority. I know meron din makakaencounter nang ganitong problema in the future, so heto ang dapat gawin after dialing *143#:
Choose My Account>Balance inquiry>Check the remaining balance of another mobile number>Enter mobile number omitting 0 (10 digits lang kailangan, so start with 9XX-XXXX-XXX).