Airtel — Not providing gst invoice for recharge payments

I did an airtel recharge for 699 on november 29 2021 for which no gst invoice is present on airtel thanks app.This recharge was done using amazon pay balance.A similar recharge of rs 699 was done in january 2022.I am asking airtel to send me gst invoice for this .but airtel customer care says they can not provide that.also I tried to reach them on twitter by personal message.I am not getting any reply from them.why airtel can not share gst invoice for third party payments.