Gmail: Email Receipt Limit due to Third Party Spam. How to fix?

Question

gmail

Our email address, which works through G Suite Gmail, was deliberately attacked - the attackers sent spam, indicating our email address in the "From" field. We have SPF and DKIM set up correctly, so these emails didn't reach anyone, but we received tens of thousands of emails saying that spam emails weren't delivered to recipients. Due to these emails, our mailbox has completely reached its hourly/daily mail limit ( https://support.google.com/a/answer/1366776), and now everyone who wants to write us a message receives an error email in response :

SMTP error from remote mail server after RCPT TO::
host aspmx.l.google.com [173.194.222.27]: 550-5.2.1 The user you are trying to contact is receiving mail at a rate that
550-5.2.1 prevents additional messages from being delivered. For more
550-5.2.1 information, please visit
550 5.2.1 https://support.google.com/mail/?p=ReceivingRatePerm h11si2947192ljb.305 - gsmtp

We think that such spamming was done intentionally by our competitors in order to bring our mailbox under the limit, and we were not able to receive new messages from our users.
How can I increase this limit or somehow solve the problem in a different way?