Hello Geeks
i would like to know if there is a way to Bond Multiple Internet WANs using multiple service providers and get them by bonding them into 1 full speed line

for example if i have 4 2.5Mbps lines to combine them for becoming full speed of 10Mbps Line

if not

Load balance so that when 1st line is full start taking from second and third and forth

if there is a way to combine them into one session

Bonding is possible only if your ISP is willing to cooperate. It requires that there is a shared public ip between the lines. I've done this a couple of times many years ago.
Load balancing is something you can do independent of the ISP. There are a few howtos around the forum and/or wiki about how to do it.

i have multiple subnet dedicated ips from the main ISP i am taking bandwidth

if i contact all 4 ISPs what should i ask them for

You'll need to ask if the 4 of them are willing to cooperate with each other in order to provide you bounding of their lines. I'll guess they say no, if you're lucky enough to get in touch with anyone at their customer care who understands what bounding is.

When I did this I had two lines from the same ISP and I pointed out the bounding requirement before ordering the lines. The ISP had never done such config before, so they struggled a while to get it working, but the final result was good. Same subnet on both lines, combined bandwidth, and when one line failed the only way I could tell was that the bandwidth was no longer combined. As for my configuration I just made a bridge-wan and added two ports (one for each line) to the bridge.