First off, those numbers are just the speed of the connection at the instant communication was established. Speeds can, and will, vary depending on huge numbers of factors.
As to your question, my guess would be that the charge from the lightning may well have damaged more than just your modem. As just one example, it could have caused the copper wire to heat up sufficiently to melt away some of the insulating plastic, allowing for some crosstalk interference from other lines to bleed into yours, making higher speed communications unreliable. Call the phone company, and try to get them to have someone come out and inspect the lines. Electric charges travel both ways in a wire after all, so it may have damaged some of their equipment.
lighting came in phone line .ive installed another modem,i used to have a varyihg download kbps.that was rangeing from 26.4 to 44.6kbps yes im on dial uo . sinse ive installed new modem i cant get any higher than 26.4 does any body know what i can do to get my speeds back up.if they do.please email me at jwaltersjr103@yahoo.com it is 56k modem v.92

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