I think you misunderstand me. I know you have a right to a refund if there is an unnotified change but I am recommending not to exercise that right if only anything bar the amount is wrong. Otherwise you will still be in debt to the company.
That wasn't what you said. Your words implied that the Direct Debit Guarantee only covers changes in amount, which is incorrect.
Even for a change of amount, I'd ring the company for an explanation first unless they've done something crazy like debiting far more than the sum you believe you owe, leaving you overdrawn.
There are two completely separate sets of legal rights and responsibilities here. One set relates to the contract between the individual and their bank, which incorporates the Direct Debit Guarantee. The second set relates to the contract between the individual and the supplier of goods and services. It is your right to activate the Direct Debit Guarantee as an account holder, but doing so does not affect the right of the supplier to the money you owe them. It's better to sort out any dispute with the supplier over the sum owed at the earliest opportunity than to use a right to snatch back your payment and wait for the supplier to pursue you.
The Direct Debit Guarantee is a safeguard but not, I'd argue, the first port of call for most problems.
Or are you saying a refund from the bank under the Direct Debit Guarantee does not in turn result in a chargeback from the company?
I have no idea where chargeback comes into this, unless you're using the term by analogy to credit and debit cards. If you activate the Direct Debit Guarantee, you are refunded and the supplier is ultimately debited the same amount.
I'm not familiar with exactly how the mechanism works, other than I believe successfully activating the Guarantee obliges your bank or building society to refund you, and this refund is final. The bank or building society then has to pursue the debiting party to get their money back - I believe organisations authorised to operate Direct Debits have to deposit some sort of security with their bank to cover Direct Debit Guarantee claims.
If I'm right about the way the Direct Debit Guarantee operates, it's more like section 75 Consumer Credit Act 1974 (groan) than chargeback. With s. 75, the debtor has the option of making the creditor severally (i.e. solely) responsible for sums due in breach of contract or as a result of misrepresentation, in which case any dispute raised by the supplier only affects the bank's right to recover their losses from the supplier. With chargeback, the cardholder only gets and keeps their money if the claim made on their behalf against the supplier succeeds. A chargeback initially credited under the card scheme's rules can be challenged by the supplier - if such a challenge is successful, the sum is redebited from the cardholder's account.