Lowes Credit Card Contact Number and Email Address

My complaint is the cancellation of my credit card. I just got approved for a credit card in May 2018 and have used my card several times. I go to purchase some items again at Lowe's to find out that my credit card had been cancelled. I have not gotten any letter stating that my card had been cancelled. I find out when I go to make this purchase. I called and talked to several people from the customer service in the credit department. I was informed that my card was cancelled because of my low card score. If that was the case, why was I approved for credit in the first place? My credit scored should not have any bearing on my account after I was approved for credit and have been using my card. I feel this is unfair practice toward your credit customer. Now if this had happened at the time I applied for credit I would understand the logic, but not after I have been approved by your credit approved search. I would like to get a logical explaination as to why my card was cancelled afrer being approved.