Please supply open invoice immediately, if it really exists!! If you fail, my lawyers will contact you to discuss further steps

Received a sms today (a Saturday, so of course when I phone the supplied contact number - nobody answers!!) about instructions to issue a summons. Regarding a payment due to LexMEd for Drs Frankel & Partner. I am not aware of any open invoice, I am not aware of ever using a Drs Frankel & Partner or LexMed for that reason. I really would appreciate to receive information about any open accounts, if there are any, before I receive a summons!! What kind of bullying is that !!??