Hi before last month I recharge 100 qr flex card...

Hi before last month I recharge 100 qr flex card before ending month I had 800 flex something pending so I again put 60 qr flex card and this month I had 747 flex pending which are valid until 2/5/2020 so I recharged again 30 qr flex card to carry my flex and I receive a msg that I have 927 flex valid till 14/5 /2020 but today they deducted my 727 flex can I know the reason