Deliberate damage.
WHAT IT LOOKS LIKE
Several negative reviews in a short period Reviews with no transaction detail Accounts with no history Reviews appearing after a dispute
WHAT TO DO
Document them: dates, accounts, content
Report them with the grounds stated Respond publicly and calmly
WHAT NOT TO DO
Retaliate with reviews of your own
That is both wrong and traceable, and it makes your position worse.
WHAT TO SAY PUBLICLY
Nothing accusatory.
A factual statement that you have no record of the transaction.
WHAT TO AVOID
Naming a competitor publicly without evidence.
That risks a legal problem of your own.
IF IT IS SUSTAINED
Take advice. Persistent deliberate damage may have legal remedies.
WHAT PROTECTS YOU
A large base of genuine reviews.
A handful of false ones among many genuine ones does little.
WHAT TO DO LONG TERM
Keep asking genuine customers.