Let the sim delete his profile from dating site on the computer, it will significantly reduce the phone calls and gifts.
That made no difference in my game as my sim never had an online dating profile. The calls and gifts were from every damned sim he/she met in person, hell they didn't even need to officially met them, and they started sending crap. Total overkill, but not surprising given that EAxis don't seem to know what the fuck they are doing. Whoever thought this would be a good idea should have been fired.
I use a mod I found at MTS, can't recall if it is the shimrod mod or not, but it works a treat, the only love letters now are in response to my sim writing a love letter.