First Great Western staff are set to walk out in a row over the dismissal of a colleague.
Members of the Rail, Maritime and Transport (RMT) union at First Great Western will strike for 24 hours from 4am on Friday and 48 hours from 6am on Easter Sunday.
An overtime ban will also be held on Friday.
Train drivers, guards and train managers based at Penzance in Cornwall are involved in the row, the RMT said.
The announcement comes in the same week the rail company was awarded a 42-month extension on its franchise by the Government.
The treasury minister has said that nurse Edith Cavell showed "true bravery" by helping injured soldiers in the First World War.
Treasury minister Nicky Morgan said: "She showed true bravery by helping injured soldiers, regardless of their nationality, and it is right that she should be honoured as a British hero.
"She risked her life to help Allied forces escape and in doing so paid the ultimate price. It is important that we remember the sacrifices made by so many people in different ways during the war."
A British nurse executed by the Germans during the First World War is to be featured on a new commemorative £5 coin. The Edith Cavell coin will form part of a commemorative set to be issued next year by the Royal Mint marking the centenary of the war.
Miss Cavell worked as a nurse in German-occupied Belgium where she helped save the lives of soldiers from both sides.She was shot by a German firing squad for helping Allied soldiers to escape across the border into the Netherlands.
First Great Western is advising rail passengers between Oxford and London to use alternative services following serious flooding.
Tickets are being accepted by other train companies operating in the area.
Train services connecting Cornwall with the rest of the country are still severely delayed after a section of the line was undermined by large waves in Devon.
Some branch lines are operating but severe weather is causing major disruptions across the network.
First Great Western continues to run a limited service between Exeter and Penzance in Cornwall after the sea undermined a stretch of the track at Dawlish.
As with yesterday, some of the branch lines are operating, but services in and out of Cornwall are very limited.
First Great Western has advised that there will be no services along the main train line connecting Cornall with the rest of the country until at least 10am.
Some branch lines are still operating although many have a reduced service.
First Great Western are currently offering no rail or road services between Exeter and Penzance, effectively cutting off Cornwall and parts of Devon. Some branch lines are still operating.
The situation will be reviewed this morning and some services could resume after 9:30am, the company said.
First Great Western has tweeted:
First Great Western is reporting delays of up to two hours as a result of speed restrictions on many routes: