Shellco Credit Money ripoff? Unknown, Ontario

Is Shellco Credit a legitimate company? They told me they so not accept credit cards... Only certified cheques issued by your bank (or cash obviously). The woman said I had to pay by the end of the month or it would appear on my credit statement. She said she has not pulled up my credit report yet but I HAD to pay it by the end of the month like I said and if I were to set up a payment plan (which she said WAS possible), it would affect my credit rating. If anybody knows details, PLEASE letme know because if this is legitimate, I have 9 days now to get the money to the company. Thanks very much!