Actually, wait, I take this back, based on a reading of the complete rule #46 (which I misinterpreted because the quote didn't include the first part):
C: If new chip(s) are added silently and the bet is unclear to the house, the call and raise rules 41-45 apply as follows: 1) If prior chips don’t cover the call AND are either left alone OR fully pulled back, an overchip is a call and multiple new chips are subject to the 50% raise standard (Rule 43). 2) If prior chips are partly pulled back OR if prior chips cover the call, the combined final chip bet is a raise if reaching the 50% standard (Rules 43 and 45), if less it is a call. See Illustration Addendum.
The examples section of TDA confirms the Call idea:
Rule 46: Prior Bet Chips Not Pulled In, situation examples.
Situation 1: If prior chips don’t cover the call AND are left alone. Ex: THE 25-50, the BB posts two 25’s, button raises to 600 total (550 more to BB).
1: Adding an overchip is a call (drop a 1k chip onto the two 25’s).
2: Adding multiple new chips is a call if all
new chips are needed to call a) drop two 500’s onto the two 25’s or b) drop a 100 and 500 chip onto the two 25’s. In these two examples all
new chips when combined with the prior chips are needed to make the call.
3: Adding multiple new chips is a Rule 45 multiple chip bet if one of the smallest
new chips is not needed to make the call (drop a 1k and 500 chip onto the two 25’s is a total bet of 1550). Per Rule 45, a silent multi-chip bet is a raise if it hits the 50% threshold; otherwise it is a call.
But again, the OP is in a cash game, so RROP may apply. RROP #15 is a bit ambiguous, as it doesn't differentiate between adding to an already existing bet amount (BB) or facing action with no chips already committed to the pot: But the wording also seems to result in a Call
#15 : If you put a single chip in the pot that is larger than the bet, but do not announce a raise, you are assumed to have only called.