when try to decrypt File Signature invalid

Hi

we are using pgp command line to encrypt files and sending to bank when bank try to decrypt file they get signature invalid . the below it's our steps that are using 

1.pgp --gen-key "SAICO-Pub" --key-type RSA --bits 4096 --passphrase "my passphrase"

2.export our public key and send it to bank 

3.import bank public key 

• pgp --import "Bank_public_key.asc" 
• pgp --sign-key 0x4F28B7F4 --signer 0xED7E8048 --passphrase "my passphrase" 
• pgp --set-trust 0x4F28B7F4 --trust complete

4.encrypt and sign file

  pgp --encrypt "E-PAYMENT-1.txt" --recipient "Bank_public_key" --sig "E-PAYMENT-1.txt" --signer "SAICO-Pub" private --passphrase "my passphrase"