Yes, if you had a Hugh backlog of calls it could slow your phone by using up a lot of storage!
Do you delete your cashed storage on a regular basis?
Your cashed storage is not your important data, it is simply what you have done with your apps!
This cashed data could accumulate and exhaust your free storage, and slow down the function of your phone!
You should clear it on a regular basis!
As I said in one of my previous posts, I am disabled. I rarely use the phone for anything except phone calls & texts. Because I cannot use my hands, I have to use my head against a button to make calls & texts for this function. It is far easier for me to use a laptop than the phone for other functions.
I haven't deleted my cache storage since I got my phone some years ago. Can you give me step by step instructions on how to perform this on the phone please?