Possibly. If your financial situation deteriorates, you can contact your Licensed Insolvency Trustee to try and amend the agreement. The trustee will help you assess your new circumstances to determine the new payment you can afford. Then they will reach out to your creditors to get their approval. As with the initial proposal, the amendment must be approved by a majority of the creditors holding the debts you owe. If they approve it, then the amended proposal takes effect and your payments would be reduced.
There are no additional fees for amending a consumer proposal.