It is generally not the case that opening a certificate of deposit (CD) with a financial institution, such as American Express or Discover, will automatically increase the credit limit on your credit card. Credit limits are typically determined based on various factors, including your credit score, credit history, income, and debt burden. If you are interested in increasing your credit limit, you can try contacting your credit card issuer and asking if they are willing to increase your limit. In some cases, they may be willing to do so if you have a good payment history and meet other criteria. However, there is no guarantee that they will agree to increase your limit, and they may require you to provide additional information or documentation before making a decision.