A number of retailers, including L.L.Bean, Crate & Barrel and Sephora, improved their speed compared to the pre-Black Friday period in November. Neiman Marcus, which saw answer times of 13 minutes earlier in the month, significantly cut down its time over Cyber Weekend to land in the top 10.
Neiman Marcus spokeswoman Ginger Reeder attributed the company's performance boost to hiring associates earlier in the season, so they would be more skilled at handling planned increases during peak times. She added that training was still going on in the beginning of the month.
"The improvement [among these retailers] is great, because the improvement says that they forecasted correctly," said Kevon Hills, vice president of research at StellaService.
Read MoreRetailers weren't prepared for mobile surge
But it wasn't smooth sailing for all retailers. At Apple, one of StellaService's callers waited more than 15 minutes to reach an agent; at electronics store Newegg, only 55 percent of callers were able to get through within 20 minutes. (StellaService abandons the call after 20 minutes). GameStop did not answer any phone calls within the 20-minute timeframe on Black Friday or Cyber Monday.
GameStop spokesman Joey Mooring said the company experienced a "significant increase" in customer calls during the Black Friday and Cyber Monday weekend.
"At times there was an increase in wait time for calls, as we make it a priority to address and solve each customer issue that we receive," Mooring said. "As a result, some calls may take longer than others depending on the nature of the call."
None of these other retailers immediately returned a request for comment.
Best Buy, whose website suffered a series of outages over the Black Friday sales period, left one caller hanging for almost 18 minutes when its site was down on Friday morning. But the electronics chain picked things up over the remainder of the weekend, posting an average wait time of about four and a half minutes over those three days.