It's a good router but perhaps not the very best in hanging on to a less than perfect line to the internet
You don't say how far away from your telephone exchange you are or what your ISP has actually done to check that everything really is OK. Often, it can look ok from their end but in reality things may be different
You may care to mull through this
will tell you what is actually happening on your line but what I would say is that, if you don't want to immerse yourself in this stuff (which can over the course of time turn you in to a gibbering wreck of a geek) there are two things to try
First, put your old router back and see if the internet connection problem resolves. Some Netgear routers have a high ability to hang on to poor internet connections far beyond the ability of other makes
I could guess which router your old one was. Can you tell me?
Second, log the statistics on router stats lite for a few days and see what your SNR margin is. You'll see where the drop outs happen. The DLink may have trouble when the margin goes below 3. The Netgear will, I suggest, hang on longer
Let's know how you get on