Help Help on how to avail Gfn softbank jp

[trololoxp15]

Since nag price drop ang gfn priority membership fee sa softbank from 1980 yen to 550 yen which is roughly 215 pesos, balak ko sanang mag subscribe pero olats sa payment option dahil Gcash amex lang meron ako at nag e-error sa billing.

May nakapag avail na ba dito using gcash amex? Need help. tia