First and foremost their customer service is quite bad. It seems that the company as a whole has little respect for their customers and will charge you more than they should hoping you won't say anything.
There is no simple way to just increase, decrease or pause account spend. We went through a tight month after using them for about 1–2 months and just wanted to pause or lower the campaign spend until finances stabilize again. I also wanted to give Analytics a month or two to see if any of the traffic they brought in that took 2–3 months to convert because their initial conversion rates were very low. There was no option to cancel or pause through the interface (which is what all others such as Google, Facebook, Adroll, etc. do), so I sent them an email asking to cancel my account. Instead, they put it on sleep mode and charged me $20 without telling me that this is what they were going to do. I had to get them on live chat to get them to delete my account (which is oddly the only way they will stop charging you) during the time they tried to sell me on just pausing my campaigns which will automatically put things in sleep mode but I declined and asked them to simply delete the account.
A few months later I decided to try them again with a different campaign to see if the results would be different. After a month of using them, I saw the same results: pretty cheap clicks, some increase in Instagram followers but very low conversions as well as some discrepancies in their stats and what Analytics show.
This time I did what they recommended last time: I paused all my campaigns to put it on sleep mode so that I could monitor the results after another month or two goes by as we do have a longer than normal sales timeline due to the nature of our products.
I was surprised to see that they instead charged me the full monthly fee of $100 instead of the sleep mode rate of $20. I had to go on live chat to get them to refund me.
Unfortunately, it seems like I'm not the only one experiencing problems with their charging mishaps. My credit card company froze my account due to the large amount of complaints they received from customers about Needls which meant I then had to call my credit card company and get them to unfreeze my card.
After all of these mishaps I experienced as well as the negative reviews I've seen from others who had similar experiences (which now seems to be more than simple mistakes on their part) it now seems to be a part of their short-sited business model of overcharging customers hoping to convince them to stay longer rather than respecting their concerns.
I've decided to just go ahead and cancel my account with them completely. It just isn't worth dealing with them anymore.
Unless you have a large marketing budget and a short purchase cycle from customers and/or you just quickly want to build up your instagram followers I'd suggest you avoid them. There is just too much shadiness to go along with their higher-than-normal monthly and weekly minimun charges.