You are to be congratulated on your disciplined efforts to understand the sources of client dissatisfaction and resulting client loss. You rightly recognize that the next challenge is to arrive at permanent solutions rather than temporary fixes.
In the same way as you have arrived at a root cause of customer service provided by your service teams, use your actual data -- perhaps customer complaints, or information provided by client loss -- to lead you to effective approaches to solve this issue permanently. For instance, when you let your data "speak," you may discover that certain innovative products win over the majority of new customers. You'll likely see an 80/20 relationship: 80% of new customers are drawn to 20% of your newly-designed products and services. Then, should training be the obvious solution (or job aids, or selective automation), then you can cost-effectively focus your training program on the 20% of products and reduce the vast majority of customer complaints.
You also suggest that there is a disconnect between the creation of innovative products/services and the process to maintain those offerings. A solid design methodology, with significant and effective up-front planning, addresses all of those concerns such that no crises will develop at roll out. A design methodology (there are several) will address these issues for your bank in the future. Design for Six Sigma (DFSS) is such a methodology that many large organizations have used successfully when designing new processes or fixing badly broken processes.