Google tells me that there are women out there named Cimberly. Cimberly is meant to be a variant of Kimberly, but when I see it, I can’t force myself to say anything but Simberly.
That’s because the pronunciation of the letter C depends upon the letter that follows. When C is followed by E, I or Y, it’s typically soft (cell, city, cyst). Otherwise, it’s hard (cat, cot, cut).
Same with names. Carson, Cordelia and Curtis have hard C’s; Cecilia, Cindy and Cyrus have soft C’s. (The only exceptions I can come up with are Irish names like Cillian and Ciara.)
If you want to personalize a name that features the letter C, be careful. You don’t want to turn Caleb in Celeb, or Cassie into Cissie. (Caleb might like the change, but I don’t think Cassie would appreciate it.)
And if you substitute a C for a K or an S without considering what letter comes next, you run the risk of turning Kent into Cent, or Sage into Cage. Or Kimberly into Cimberly.