World Financial Capital Bank/Blair Added interest payment to a paid off account , Internet

My mother ordered items from Blair Company. She returned some but kept some. People at Blair Co. told her the amount due and she sent a check immediately. The check was cashed and returned to her bank. On May 22 my mother received a telephone call from a collector at World Bank. He told her she owed about $60.00 in interest. She said she owed no one and wanted to get to the bottom of this. The collector then told her to contact Blair Co. to acomplish this. In contacting Blair Co, I spoke with a lady named Loraine. She said that my mother owed them nothing and that I should contact "world bank" to try to get things straightened out. She also said the only thing possibly owed was $8.00 for shipping but that's the most it could be. I finally was able to wade through the ten minutes of telephone options and contacted a foreign speaking woman named Alma. This World Bank is in San Antonio Texas. The first thing Alma told me was I needed to talk to Blair Co. I told her that Blair Co.said I needed to talk to them. I was unable to speak with a supervisor since I needed my mothers authorization to talk about her account. I will accept this argument today, May 24, but will again call tomorrow with authorization and try to clear this up. So far the whole thing seems like a corrupt way to steal from the elderly.